Teardown, Modification: Sony AN-LP1 Active Loop Antenna

When an engineer isn’t happy with something, they often try to “fix” it. Sometimes this ends up in hilarious failure where the said object becomes more broken than when they started. Sometimes it ends up in success, but most of the time it ends up somewhere in-between. As I noted in my review of the AN-LP1, the performance of the active antenna was pretty marginal for me, so I wondered if there was a way to improve it. To do this, we first have to open it up and take a peek inside.


As it turns out, tearing down Japanese made products is relatively enjoyable, especially because all of the screws that need undoing to open the case are helpfully marked with arrows. Lets start off with a simple one – what’s in the filter unit?


Four small Philips screws later, we get our answer – it appears to be a common mode choke based around wrapping the wires around a clip-on ferrite, packaged as a fancy plug-in unit. Interestingly, because of the special connector arrangement in use, the male connector is the same moulded plug as supplied with the antenna controller box.

Getting a little more serious now, lets find out what’s in the antenna unit itself. It’s the same story – four Philips screws and we get access to …


… a PCB without any shielding around it. Hmm. Okay, taking a closer look, we can see that the loop antenna is actually formed by a thin, black-silicone insulated wire which runs around the outside of the sun-shade like apparatus. The steel “springy” wire that keeps the shade open is not used for the antenna itself, possibly because of connection difficulties. The PCB itself contains a host of diodes and FETs, the main star being the array of Sony 1T369 variable capacitance diodes which help do the tuning.


On the other side, there is a small transformer, and a through-hole inductor.

Time for the antenna controller box to get opened up – this time, five screws needed to be undone.


We are greeted with a very interesting and mesmerizing design. The antenna cable reel actually connects to the main PCB through another PCB with concentric ring tracks. The reel itself features dual-contact wipers which wipe around the rings as the reel is wound/unwound. Four contacts are available, with five contacts on the plugs – so ground between the two plugs is common-ed. Such an arrangement seems elaborate and similar to the mechanism used in generic multimeters for range selection, but I suppose that is how you would get a signal out of a rotating spool of wire.


To ensure a smooth action and good contact, the board and the spindle are coated in a conductive lubricant. The cable itself seems to be somewhat waxed for easier passage, and the flakes of wax worn off from the cable can be seen collected near the entrance hole at the top. This is the sort of attention to detail that is missing in some cheaper products.


The main board itself has an Alps rotary switch, which is a quality item. There are also a large array of variable resistors (trimpots) used to set the tuning peaks for each of the bands. The DC to DC converter seems to be shielded under a metal can which is soldered down to the board – so I’m glad they did do this to reduce the amount of interference it would cause.


The underside has another can on it, although smaller, but otherwise, it is pretty bare. Putting it all back together was pretty simple, with nothing broken in the process. Definitely a sigh of relief, because I only just got it.


Because the signal from the antenna didn’t seem to be sufficient, I surmised the main cause is the small aperture of the loop. If we look at the antenna module PCB, it looks very simple, and removing it only requires de-soldering two wires. Ignoring the inductance and impedance of the loop for now, I wondered if we could get better performance simply by using a larger loop of wire.

20151003-1152-5708I began by de-soldering the two wires to the existing loop, removing the PCB, and then soldering two new wires to it. These would allow me to connect my own wire to the PCB.

In order to make sure the PCB wasn’t damaged in my experiments, I opted to wrap it in a layer of electrical tape, and then wrap the wires in the tape as well, to provide some strain relief. The last thing I want to do is lift the pad off the PCB.


I had a reel of 0.9mm “fence wire” style galvanized metal wire. I decided to make a square loop, as that provides more wire for the same diameter. I decided to go with a 1m x 1m square, so it has a diameter of sqrt(2) meters, and the loop will total 4m of wire, which is about 3 times more wire than the included round sunshade. To make the connections, I used a screw terminal connector block, as soldering to such galvanized wire is a pain in the butt. The wire itself wasn’t very stiff, so I had to resort to finding something to support the structure of the loop. In the end, the best thing I had was an insulated fibreglass pole antenna for 27Mhz CB, which was about the right length. The corners were electrical taped to the antenna to ensure it physically held its shape.


Initial results were encouraging. Powering it up and tuning into the BoM’s VMC radiofaxes seem to show marked improvement, with the reception performance now indistinguishable from my 15m longwire outside.


In the course of this fax, I swapped back and forth between the two inputs on the Icom IC-R75 and found no meaningful difference – both antennas were subject to fading and weak signals, but both performed equally well. I added a coloured bar on the side to show when the antennas were switched. This was a welcome change.

But sadly, this change was not without caveats. For one, I found that higher frequency tuning was not possible. The range selector for 4-7Mhz worked correctly, but above that, the selector settings for 10-20Mhz instead only pushed a range of 8Mhz to 13Mhz. This limited the usefulness somewhat.

It seems that this may have arisen because of a dependency of the board on the inductance of the loop. The service manual claims that tuning has to be done with a dummy 2.2uH inductance, so I suspect the loop needs to have the same inductance to make it work properly.

There could have been some way to improve on this, by adjusting the tuning voltage pots on the antenna controller, but I didn’t want to create further problems right now. Looking at some datasheets, I’m not convinced that this would open up the range that is necessary – for one, the DC-DC converter in the controller has a limited output voltage, and the variable capacitance diodes also have a limited operational voltage. This is already 17V at the 20Mhz setting, and the diode itself has a maximum operational voltage of 28V. An increase of 11V doesn’t really change the capacitance very much, as read off the graph:

Voltage   Capacitance
1V        58pF
10V       10pF
17V       4pF
28V       2.8pF

As a result, I don’t think tinkering with the potentiometer on the antenna controller would have been wise. Regardless, maybe changing the inductor values on the antenna board would be more productive, but I didn’t want to break it just yet.

I was thinking – “wouldn’t it be nice to shove the board in a jiffy box with two 3.5mm connectors for each antenna pad, and just use any pre-made length of 3.5mm to 3.5mm cable as a loop?” Evidently, things are not so simple. Bummer. But a 1m x 1m loop indoors was able to work as well as a 15m longwire outdoors – that was an interesting result in itself. Maybe the cheaper Degen DE31 might be more amenable to this sort of modding, but I suspect we will come up towards the same barriers of the loop’s inductance causing some limitation in tuning range.


The motivation for the modification was pretty obvious, and upon tearing down the unit, the most obvious thing to do was to increase the loop aperture by connecting it to a larger loop of wire. While that was done, and the performance did improve markedly, there was a side effect which resulted in a limitation of tuning range, with the selectors for 4-7Mhz working as expected, and 10-20Mhz instead selected a range of about 8-13Mhz instead. Despite the presence of a service manual, and the possibility of re-tuning the tuning voltage to try and get a little more range, I suspect there would not be a full recovery of the range purely because of the limited voltage output of the DC-DC converter and the voltage limits of the varicap in use. As a result, I am a little disappointed, but I’ve restored the unit to the original configuration, unharmed for now.

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Review: Sony AN-LP1 Indoor Shortwave Active Loop Antenna

One of my plans after I finish my PhD is to take some time off and travel the world. Being an engineer at heart, I don’t just take “regular” holidays – I need to bring my hobbies and experiments along. For radio enthusiasts, some take holidays just to chase down signals, something they often term a DXpedition. While I am not as dedicated as that, I still think it would be nice to sample the radio spectrum at different places around the world “while I’m there”, laws permitting (of course).

A particularly challenging portion of the spectrum is HF or shortwave. As I’ve mentioned several times before, Australia isn’t really the target of many signals, so hearing things down here can be a little difficult compared to Europe, where signals are ample. Even highly sensitive portable radios, like the Degen DE1103 of which I have two of, struggle to bring in any intelligible broadcasts with their 1 meter whip, or with the included ~10m of wire strewn across the room or even out a window. Some targeted broadcasts are “listenable” but hardly pleasurable.

The bigger issue in HF is noise. That part of the spectrum is particularly vulnerable to natural and man-made sources of noise – with cheap switching converters, computers, monitors, solar garden lights, poorly design light globes and Ethernet over Powerline (HomePlug) devices amongst others spewing out noise across the band which masks the signals we want to hear. Sadly, there is little we can do about this, and where signals are weak, a longer longwire antenna can end up picking up just as much noise as signal, resulting in a signal that is stronger but not any clearer.

My saviour has always been the Wellbrook Communications ALA-1530L – a shielded magnetic loop antenna that looks a little like a shiny rigid aluminium basketball hoop, of about 1 meter in diameter. It pulls in signals which are buried under the local noise much better than anything else, but it is very expensive (especially due to our falling exchange rates) and it is, for the most part, not something you can pack in your luggage and fly off with. It would be nice if it were possible though! Since then, there have been numerous improvements to the design, although tempting, I don’t quite have the pockets for it at this time.

So what is a traveller supposed to do? If you’re in a hotel, chances are that there’s a million LCD TVs, variable speed lift motor drives and light globes in close proximity spewing noise to oblivion. This means your regular telescopic antenna is probably hopeless, along with amplified regular whips. Often, because of vertical construction, you don’t have more than perhaps a balcony to use to put an antenna out, and hanging a wire over the edge just doesn’t seem like a good idea.

While trying to work out the answer, I came across several amplified loop antennas designed for travelling. One is the cheaper Degen 31MS, which is made with a soft wire loop, is about AU$30 but looks flimsy with a touchy tuning wheel and mixed reception. Aside from that, there is the Sony AN-LP1 Active Loop Antenna, which has better build quality, some innovative features and better reviews, but is only available in Japan and is much more expensive. Luckily, we have eBay, so AU$130 and about a month later, I managed to buy one and run it through its paces to see what it is capable of.

Unboxing and Set-Up


20150930-0051-5633 20150930-0051-5634

The product, similar to some other Sony products, comes in a relatively bland cardboard box with monotone printing. The box itself is around the size of a hard-cover novel. Rather encouragingly, the product is Made in Japan, so we’re definitely expecting quality. The J on the label, I believe, indicates Japanese market product – the AN-LP1 doesn’t appear to be available anywhere outside of Japan. The antenna claims coverage from 3.85Mhz to 21.95Mhz.


Included inside the box is two carbon-zinc style AA batteries (so you can get started immediately), a telescopic whip adapter, and a drawstring bag containing the antenna units.


Also provided is several pieces of paper, including an instruction manual copyright dated 1997 (making this product design 18 years old), a warranty registration card, some warning and support guides and an instruction manual for the included filter module.


Inside the bag, we find the antenna module itself, which has a suction cup for mounting on windows, or a clip for hanging on blinds. The clip itself is very sturdy and capable of hanging onto most things. The antenna itself seems to be modelled on a foldable car sun-shade, and is shown in the stowed and clipped position. To the right is the in-line filter unit.


Also included is the antenna controller unit, roughly the size of two stacked cassette tapes. The big wheel is the retractable antenna cable winder, with a slide switch and LED for power, and a rotating selector to choose the centre frequency of reception. It feels relatively solid, and the winder is smooth to operate.


The unit is powered by two AA batteries (included, as above), and internally stores the antenna cable in a spool (about 4m length). The output from the unit is fed out to a mono 3.5mm plug via a cable that wraps around the edge of the controller and nestles in a cut-out in the bottom right of the image.


The connectors themselves are moulded and Sony branded, and is generally “idiot proof”, however, the wires are quite thin, so care should be taken when pulling them in and out. It also seems that the antenna cable has been waxed for additional lubrication, and when rewinding, wax accumulation can be seen at the edges of the casing. It’s nice to see the attention to detail.


When set-up, the antenna looks like a sun-shade or an oversized microphone pop-screen.

Connecting it Up?

As the output of the antenna controller is to a mono 3.5mm jack, intended for Sony portable receivers, connecting it to serious reception gear that has a BNC or SMA coax connector seems to be something that’s not straightforward.

20150930-0028-5631I reasoned that the connector is often used for external long-wires to be connected to the radios, thus, is a high impedance input. So therefore, we should probably treat the output of the antenna as a high impedance signal. This means we should use a longwire adapter. It’s probably clear why I bought another one … to modify. First step was to remove the banana jack, and replace it with an old fashioned 3.5mm mono jack (from my scanner discriminator mod days). The hole itself has to be drilled to 6mm to accommodate the jack, which is then screwed into place and soldered.

This does leave the question, what about the ground? In fact, the ground should be common to both jacks, so I decided to get a piece of short insulated wire to bridge them together.


With this interface, the 3.5mm mono plug can be converted to a BNC output for feeding a proper receiver with convenience. I decided to go one step further and fill the inside of the box with silicone, except the area around the 3.5mm jack so that it can still fit in. This will provide mechanical rigidity to the ferrite toroid and wires, so they don’t break under mechanical shock.

Of course, I thought I did the right thing, so I tested it out with my Tektronix RSA306, using it “directly” connected to the analyzer input (top) and via the longwire adapter (bottom).

direct lwa

As it turns out, the signal seems to be marginally stronger with it directly connected. The high frequency noise also seems to be lost with the longwire adapter. Hmm. Maybe the amplified nature of the antenna has an output impedance low enough to drive a 50 ohm input directly … and all of this is in vain?

Of course, if you’re using a portable receiver, it may well have an external antenna jack which would be the right fit, or you can use the included conversion clip which clips onto the telescopic antenna itself.


While I was at it, I decided to compare the two longwire adapters with the output from the Sony loop, flipping between the tuning settings – in all, it again seems to confirm that the WiNRADiO is marginally better, but not in any big way.


Filter Operation

The included filter unit did arouse some of my curiosity – did it have any noticeable effects? The Tektronix RSA306 seemed to answer that with a definite yes.

4Mhz-NofilterNo Filter

4Mhz-SettingWith Filter

It seems there is a spike of interference at about 8.5Mhz which is much attenuated by adding the filter module in-line as described by the yellow leaflet. This may be because this is local electrical interference which is getting into the retractable antenna cable which is not shielded and the filter is acting as a choke.

Frequency Selector Operation

Lets see what happens as we twist the frequency selector dial.

4Mhz-Setting4Mhz setting

5Mhz-setting5Mhz setting

6Mhz-setting6Mhz setting

7Mhz-setting7Mhz setting

10Mhz-setting10Mhz setting

12Mhz-setting12Mhz setting

14Mhz-setting14Mhz setting

16Mhz-setting16Mhz setting

20Mhz-setting20Mhz setting

It’s clear that changing the frequency selector dial does impact on the peaking of the signals from the loop. In this way, the loop itself acts as a pre-selector, only really amplifying the frequency band which is selected. The bands are narrower towards the low-end of the spectrum, and it seems more gain is available, whereas towards the higher end, the bands are wider and the gain is somewhat reduced. It seems that the loop also handles decently strong MW transmissions just fine, with them attenuated to a satisfactory level (although, this unit is not specified for MW reception at all).

As the tuning switch is fixed in its selections, it is not possible to continuously drive the peak to any frequency from the controls provided. This may mean that the reception is sub-optimal for some frequencies within the bands, and possibly, very sub-optimal for between-band frequencies.

Electrical Aspects

A quick electrical check of the connections – of which there are five – had me concluding the following:

  • 3.5mm mono jack – tip is battery +’ve, ring is ground.
  • 2.5mm stereo jack – tip is tuning voltage +ve, ring is tuning voltage ground, and sleeve is the antenna signal.

Therefore, the 3.5mm plug carries power from the batteries (it’s always ~3v regardless of the frequency selection), whereas the front two contacts of the 2.5mm plug carries a tuning voltage – 1v at 4Mhz, and 14v at 20Mhz. This is probably used to drive a varactor or similar to control the frequency peaking – which theoretically could be anywhere provided a continuously variable voltage is produced.

As the unit is powered by two 1.5v cells, there must be a switching converter of some sort inside the unit to provide the higher voltage required for tuning. This leads me to believe that some of the observed interference spikes may not be local interference from electrical appliances, but could also come about due to leakage of the switching waveform harmonics into the RF chain.

A quick check of current consumption showed that the unit consumed 10.07mA at 3v, thus a set of alkaline batteries can be expected to last well over 160-200 hours of operation.

Subjective Tests

From connecting the antenna to my Degen DE1103’s external antenna jack, it seems that the signals are received less strongly than with the telescopic whip indoors. This might be due to the relative gain difference, as using the telescopic whip adapter seemed to provide better results, although interference was troublesome with the DE1103. Throwing out a long piece of wire indoors picked up more noise – so the loop antenna seemed to have an advantage when it comes to local interference.

Using it with the longwire adapter and my Icom IC-R75, I could easily compare the performance of the loop indoors (ANT 1 input) and the 15m longwire outdoors (ANT 2 input). On the whole, the longwire outdoors beat the loop indoors every time, and the difference was quite noticeable even on local broadcasts (i.e. Bureau of Meterology weather voice and fax). This is particularly disappointing when we consider that the Wellbrook loop, also outside, outperforms my 15m longwire with a noticeable margin too. As a result, the Sony loop doesn’t seem to collect enough signal to be a good candidate for even receiving lower-powered local transmissions. This is clearly reflected in this local radiofax received with periodic antenna switching from internal (noisy, dark fades) to outdoor longwire.


On broadcast transmissions targeting Australia, the performance was acceptable and the audio was intelligible, although the noise level seemed higher than the longwire.

Using it with the longwire adapter and my WiNRADiO G31DDC was also possible, although it clearly showed the problem with “peaking”, as SDRs can have wide-band operation which exceeds the peaked reception bandwidth of the loop. The peaks seem optimized for broadcast bands, so hams and utility monitors may find lower gains where they need it most. The broadband Wellbrook is very much preferable for this reason. The signals were of no real difference, with the Wellbrook and 15m outdoor longwire preferable. If I would have to say, the performance of the Sony loop is probably about a 7.5m long-wire roughly.

The convenience is that it is easily packed, easily set-up and less sensitive to local noise, but for DXing, it is a bit disappointing. Although, that being said, as the service manual seems to be available online, there may be potential for modifications and improvement.


It’s no Wellbrook loop, nor is it even a match for a 15m longwire placed outside which is noticeably worse, but to compare it to those would be rather unfair given the Sony sits indoors – closer to sources of interference.

When using the antenna, at least in Sydney, it seems it struggles to bring in enough signal. Compared to the telescopic on the DE1103, the performance is much better. Signals which are barely discernable on the telescopic are listenable under the loop. It’s a shame it’s not “clear as a bell” like it would be on the Wellbrook. Part of the reason probably comes down to the smaller loop aperture of 50cm diameter, which reduces the collected signal. Being closer to interference is a disadvantage as well.

The tuning dial can be seen to act as a pre-selector, eliminating one of the issues with lower cost receivers in their rejection of out-of-band signals. This in itself can be of a benefit for portable low-cost radios, but is a disadvantage if you are intent on using it with wide-band SDRs. Because the tuning dial is “stepped”, accurate peaking of the signal is not possible, and only pre-tuned peaks can be selected. Broadcast-band listeners are probably not going to see significant disadvantages from this, however, outside of broadcast-bands, the reception might not be optimal.

Of course, the antenna is designed for use with Sony equipment, specifically, some models of their Word Band receivers. I did try it with the DE1103’s Ext Ant input, but found the signals to be worse than the telescopic (probably due to low gain on the external input), and thus the telescopic antenna clip seemed to work better (but then you do get some local interference to boot). Using it with more serious gear proved to be an interesting challenge – using my gut feeling of putting in a longwire adapter for impedance matching seemed to provide no real benefit to the signal output compared to direct connection, which was not particularly strong, but it was still usable with my Winradio G31DDC and Icom IC-R75. Some harmonic-style interference spikes were seen, which may be a product of local noise and/or the internal switching converter inside the unit used to generate the tuning voltage.

Regardless, it seems to be a niche product, which probably works well for its intended purpose – i.e. listening to target-area broadcasts with table-top portable receivers. For the DXer, it probably still has benefits over telescopic antennas because of its lower sensitivity to E-field interference, but it doesn’t have enough “copper” to pull in the weaker signals as a longwire would. If travelling in strong reception areas, it will probably be enough, but for DXing, it seems it isn’t really an optimal choice.

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Review, Teardown: Unbranded “Generic” vs WiNRADiO WR-LWA-0130 Longwire Adapters

Anyone who wants to listen to shortwave radio, or monitor high frequency transmissions, would have met the dilemma of trying to get a decently performing antenna. As it stands, most smaller radios with inbuilt telescopic antennas rarely reach more than 1m in length, and they tend to be inadequate in marginal to poor signal areas such as Australia. Worse still, they are more than capable of picking up local interference with little hope of grabbing enough signal to overcome the local noise – poor signal to noise ratios are the result.

A very simple and inexpensive antenna is known as a longwire, and as the name suggests, typically consists of a random length of long wire strewn about outside where the signal is better, being remote from the local interference. Getting a longwire to work is, however, not necessarily as simple as hooking it up.

For small portable receivers, some success can be had by connecting the longwire to the telescopic whip, although often this results in overload (i.e. signals which are too strong) resulting in distortion and signal images (finding signals at frequencies where they shouldn’t be). Some better portable receivers offer switchable sensitivity (DX or LOCAL switch) to cut down on the internal amplification (which amplifies noise as much as signals) to try and avoid this. Others offer a less sensitive external antenna jack which is often just a mono 3.5mm jack intended for connection to a longwire.

But better receivers generally don’t have such tacky methods of interfacing to an antenna. Proper RF equipment almost certainly uses a 50 ohm coax connector of some description, be it a PL-259, N-type, BNC or SMA connector. These connections are optimized for use with 50 ohm impedance sources. The problem is that longwire antennas are not 50 ohms impedance, and direct connection typically causes marginal performance due to signal losses in impedance mismatch as well as a secondary signal degradation by having the antenna itself consisting of all segments including those close to the receiver (where the noise generally is).

A way around this is to use an impedance transformer known as a longwire adapter or a longwire balun, which is typically a 9:1 impedance transformer (450 ohms to 50 ohms). Such an adapter connects to a longwire antenna (often just one connection, or one connection plus ground for better units) and offers a coax connector on the other end. This allows you to use a shielded coax lead-in that prevents local noise from getting into the antenna and allows for a better impedance match (although imperfect due to random wire length) to the longwire antenna, typically boosting signal by about 6dB.

Such adapters can be home made, but the hassle of getting the right sort of ferrite beads, connectors, and then soldering/wiring it up yourself without knowing if it’s quite right is really an inconvenience I’d rather do without. As a result, I ended up purchasing commercially made adapters for my own usage.

In this post, we will be comparing a low cost ~AU$20 generic unbranded Chinese longwire adapter with a five year old Australian WiNRADiO branded WR-LWA-0130 ~AU$55 adapter to see how well they are constructed and how well they perform with the aid of the Tektronix RSA306 Real-Time Spectrum Analyzer.

The Generic Adapter


Can you say cheap? This adapter cost just under AU$20 posted from China, and is as generic as can be.

20150930-0022-5628 20150930-0022-5629

It sits in a beige box with no branding whatsoever. A BNC connector adorns one side, with a binding post/banana plug combo jack on the other. That’s literally all there is to it.


It doesn’t take much to open it – just a quick pry at the slots and we’re in. Inside, there is no shielding whatsoever, nor any PCBs. Just a toroid with enameled copper wire windings soldered directly to the connectors, with the toroid left hanging unsupported. I’m surprised it got here without a wire detaching or the ferrite toroid being smashed into dust.

The banana jack wasn’t very well secured either – using the binding post feature could end up spinning the solder tag inside when tightened up, causing wire fatigue and eventual wire breakage.

Given the questionable looks, I wonder how it performs. The eBay listing itself stole images from I6IBE’s website, so I suppose the design itself is probably okay, and the performance will come down to construction and component choices.

WiNRADiO WR-LWA-0130 Longwire Adapter

The other contender in the head-to-head is an old reliable. This adapter has been with me for five years now, and has had a hard life. At one stage, it spent over a year outside getting alternately cooked and rained on, and it does show. But it’s always been there for me, and worked relatively well, and at a price of AU$55, it was acceptably priced.


When you look at the unit, you know it’s something proper. It has a cast metal exterior with a logo unmistakably moulded on it. The all metal exterior acts as an excellent shield.


While there’s some signs of rust, there is clear evidence of sealing around the edges to prevent water ingress. Removing the screws allows us to look inside.


It’s clear that no water has made it inside, which is a relief. The adapter itself has a PCB and seems decently supported. A soldering iron was required to de-solder the tags on the wire side, and then the BNC connector retention nut undone, to allow the PCB to be moved out of the enclosure.



The single sided PCB has two toroids on formers on the top, and thus is likely to use a different, seemingly more refined design. The manufacturing looks spot-on, with no rough edges. A very professional product.


Even the inside of the casing had silicone applied around the BNC plug entrance to ensure water would not seep past the edges. This attention to detail is what you get from a proper product from a company that knows what they’re doing.

Head-to-Head Comparison

A head to head comparison was done by using my outdoor 15m longwire, connected to one adapter at a time for a minute, with the peak hold spectra saved. The red trace indicates the result from the generic, with the blue trace indicating the result from the WiNRADiO. Of course, these results only hold true under my testing conditions – in the presence of strong RF signals, other effects from saturation/non-linearities may show up, or at different wire lengths, performance may differ.


Throughout most of the spectrum, the two adapters are very close in readings, with the signal strengths of the WiNRADiO seems to edge out the generic by about 3dB in absolute magnitude. Above 21Mhz, it seems the generic adapter seems to put through more signal by almost 5dB, but that could just be noise. In all, both adapters seem pretty much neck and neck, although I would have to give the edge to the WiNRADiO for performance and design reasons, although I probably wouldn’t be disappointed if the generic was all I had.

Interestingly, this might go to prove one of the counter-intuitive things with RF. Sometimes, a design might seem better as “on paper” it seems to solve the problem better in theory. But because of the “gap” when it comes to implementation, sometimes adding more complexity to try and improve the result actually ends up introducing more imperfections which work against you. It could be the case here that the two-toroid design with smaller toroids might have more losses than a loosely and messily wound single-toroid design causing the performance of the two designs to “converge”.

Bonus Teardown: Mini-Circuits ZFSC-2-1-75

20151001-2151-5682A while back, I purchased a hybrid type power splitter with the intention of using a single antenna amongst several receivers. Sadly, the only unit available was a 75 ohm impedance unit, which isn’t ideal for 50 ohm systems (mismatch causes loss), but I decided to get it anyway. The antenna output signal wasn’t sufficient to overcome the -3dB splitting loss, insertion loss and impedance mismatch loss, so I counted this as a write-off, but it’s worth looking at how a reputable company constructs its splitters as a key to how RF products should be manufactured (contrasted with mass-market units, like this).

The unit itself is made completely with a metallic body, forming a low impedance ground path and shield across the active internals. The unit is held together with two screws, which are easily undone to reveal the insides.


The inside shows the three inputs neatly lined up on a small PCB with two transformers and some passives as well. The wiring appears straightforward, and neatly done.


The rear of the PCB is left un-etched and instead is used as a ground plane with plenty of solder to the shells of the connectors to ensure a low impedance ground path and consistent RF performance across the PCB.

This contrasts strongly with the low cost Chinese splitter linked earlier with no ground plane, only relying on the unit’s metal casing as a shield and ground, and hand-wound transformers with messy wiring.


In RF, the performance of devices often comes down to minute details in the design and construction of devices and their consistency. It is clear that properly designed equipment tends to be well shielded, rigidly mounted, and constructed in a way which is consistent (e.g. by use of formers, PCBs, etc).

Despite the obvious shabbiness of the generic adapter, its performance was not objectionable – which turned out to be a big surprise to me. This is likely because the unit wasn’t completely designed without thought, but also because HF frequencies are relatively low and the demands it places on dimensions are much less severe than in UHF/microwave work where hand-made often isn’t good enough.

Despite this, it is clear that the lack of shielding is a concern in RF harsh conditions, and it only really gets away with it because of the low flux leakage properties of toroidal transformers. The lack of weatherproofing and ground attachment point is an inconvenience as well, with the lack of rigid mounting making the core and enameled copper wire vulnerable to damage from mechanical shock. That being said, it’s nothing a few modifications can’t help or fix, but I suppose it wouldn’t hurt to spend a little more for convenience.

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