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Old 8th Feb 2021, 4:03 pm   #1
regenfreak
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Default 5.6m telescopic whip and ATU for SW/Ham receivers

For a long time, I had no interest in SW listening and Ham radio because I live in an apartment block surrounded by buildings in inner London with no hope of having an external antenna. But I have RTL-SDR software-defined radio. It can only receive FM with its rabbit ear telescopic V- antenna. SW is hopeless.

I have been building FM stereo radios using IC chips and got interested in the FM front end design of modern receivers. So I purchased the Tecsun R-9700DX full analogue multi-band receiver to study its FM design circuitry. It has got me interested in SW listening again.

For the first time in my life, I listened to SW indoor relying on its whip antenna a month ago. Then I bought the software-based XHDATA D-808 and the active loop MLA-30+. The long wire antenna does not work in urban environment because it picks up all the noises. The MLA-30+ certainly improves the signal-to-noises ratio but it still don't pick up distance weak stations. I mount the MLA 30+ on a long PVC pipe and on a heavy-duty studio camera triple by the window. It can rotate 360 degrees freely.

My mega long 5.6m telescopic whip has arrived from china today. My plan is to adjust its optimal length using a VNA for a particular band and stick it out of the window in the summer for SW and Ham listening. The 5.6M telescopic whip is intended for DIY V-antennas or mono-whips in Ham transceivers and not for receivers. I have never seen they are being used for receiving out of a flat's window. My questions are:

1. Can either passive or automatic ATU antenna tuning unit be effectively used for receivers? It certainly works for transmitting but I don know if the ATU effectiveness reciprocal in receiving.

2. Can a balun be used to reduce noises for an unbalanced whip antenna? I read about 1:1 , 1:9, balance and long wire balanced/unbalanced balun for transceivers but I don't know if they can be used for receiving only.

3. Will the 5.6m whip work better than the active MLA 30+?

4. If I attach a broadband RF (30 db) amp to the 5.6m, will it just overload the receivers?

5. If there is an online calculator for passive SW loop design?

I cannot try the whip until I find a way to mount it and the weather gets warmer.

I have a large transmitter variometer ( with 25 tappings and rotating coil) that can be used to peak the whip antenna to resonance frequencies and a passive ATU DIY kit that I never bother to build.

So far my SW and Ham listening experience has been discouraging. The air is well-dead. I have got a cheapo Boafeng UV-5R with Chirp programming installed plus a longer whip antenna. I can receive no HAM channel at all.


Title edited by Radio Wrangler.... ATU in place of AUT
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Last edited by regenfreak; 8th Feb 2021 at 4:22 pm.
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Old 8th Feb 2021, 6:54 pm   #2
Andrew2
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

Wires and whips are not much good indoors these days as you have discovered. The noise level has massively increased over recent years and conventional wire aerials love it.
Loops are much better, and the self-supporting type like the Wellbrook aluminium loop can be easily mounted on a pole or tripod and rotated to further null out the local noises, but Sod's Law says that as you null one noise another will come up!
I've had a Wellbrook since about 2000, and started off with it on a tripod indoors. Even that was a huge improvement on my outdoor wires, taking the noise level down by several S-points. When I got around to mounting it at gutter height at the rear of the house there was a further drop in noise.
Sensitivity is not the problem. Most SDR's are quite sensitive and adding a heap of gain in front of them usually makes things worse due to overload. To make things worse, the RTL type of SDR tends to be short of dynamic range and you are always trying to tread the fine line between internal noise and overload. There are better SDR's out there but with the general state of the bands can make it seem unwise to spend money.

Re the general lack of signals - HF propagation is very bad at the moment and has been for several years. Amateur comms are at a low ebb due to the poor conditions and anyway there has been a drift away from analogue 'phone to digital text/data like FT8.
Utilities like aircraft are still about but a lot of maritime services have gone digital, so the delights of 'Anglesey Radio, Anglesey Radio' are things of the past.
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Old 8th Feb 2021, 7:47 pm   #3
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

Quote:
Loops are much better, and the self-supporting type like the Wellbrook aluminium loop can be easily mounted on a pole or tripod and rotated to further null out the local noises, but Sod's Law says that as you null one noise another will come up!
I've had a Wellbrook since about 2000, and started off with it on a tripod indoors. Even that was a huge improvement on my outdoor wires, taking the noise level down by several S-points.
The Wellbrook is many times the price of the poorman's SLA-30 +. I have extended the 5.6 m whip indoor up to 2.9m and leaned it against the window. Its resonance peaks at around 26MHz based on the VNA sweep. It is working as good as the SLA-30 + picking more stations but also more noises. I think it will work a lot better when I stick it outside the window in the summer. It is a hot FM antenna even its length is longer the quarter/half wavelength based on the Tiny SA spectrum analyzer readings.

Quote:
Re the general lack of signals - HF propagation is very bad at the moment and has been for several years. Amateur comms are at a low ebb due to the poor conditions and anyway there has been a drift away from analogue 'phone to digital text/data like FT8.
Utilities like aircraft are still about but a lot of maritime services have gone digital, so the delights of 'Anglesey Radio, Anglesey Radio' are things of the past.
I have received no SSB, no air band, no maritime, nothing with the XHADAT D-808 indoor. The SW stations are not interesting to listen to. Last night I was listening to nuns' prayer from the Vatican Shortwave transmitted from Ukraine. That was the most interesting thing I have received. I have tried to listen to the International Space Station ISS on 145.800 MHz with my Boafeng UV-5R +, have no luck so far. At least in the USA, people can listen to police communication etc. I have invested not much money on this hobby on SW and Ham listening. It is easy to get discouraged and give up. Probably I am more interested in the technical side of antenna and theory etc. Otherwise I find it very disappointing listening experience in SW radios.
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Old 8th Feb 2021, 7:55 pm   #4
G6Tanuki
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

As noted upstream, SW reception in urban areas is blighted by 'sharsh' from modern electronic devices like SMPS and LED/CFL lights.

[But in reality is this any worse than the every-15KHz rasp from 625-line TV line-timebase harmonics we put up with in decades past?]

Tnere's a lot less to listen to on SW these days too: almost all the nation-state broadcasters [Radio Nederland, Sverige Radio, RNZ, Radio Tirana, Deutsche Welle, Swiss Radio International and such] have closed down - what remains is predominantly the likes of Radio China and a bunch of religious broadcasters - hardly an enjoyable menu.

Hams are still out there: the last sunspot-cycle was a bit of a dud but in recent times 21MHz has been showing signs of life. There's always the lower ham-bands: I operate predominantly on 3.5 and 5MHz, both of which currently offer good inter-Europe and east-coast-Transatlantic contacts especially in the small hours.
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Old 8th Feb 2021, 8:49 pm   #5
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

So the SW listening is dying? I never listened to SW growing up as a kid in 1960s so i never missed the glorious days of the Cold war SW nostalgia:

Historical recordings of interval signals from disappeared stations 1950-180s:

https://youtu.be/sf_UzdvTyKQ


It is a good read about solar winds and sun spots on RF transmission at different SW frequencies:

https://weather.mailasail.com/Franks...ems#ionosphere

I paid one year membership to join QRP UK club last year to get discount on electronic components but I have no idea what is QRP even this day. It is not possible to have a Ham hobby when you live in city and in an apartemt block. So i can only read about Ham radios but not to experience it.

Last edited by regenfreak; 8th Feb 2021 at 8:57 pm.
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Old 8th Feb 2021, 9:50 pm   #6
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

I f you have a car and are able to take a drive into the country on the weekend, then you are able to practise Ham Radio (obviously in the warmer weather).

QRP is low power level operation is is ideally suited to the above endeavour.
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Old 8th Feb 2021, 10:08 pm   #7
regenfreak
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

I built a cheap Pixie QRP DIY kit receiver three years ago when i first picked up electronics as a hobby. That was the time I knew nothing about radio engineering and bought a antenna tuner unit kit at the same time. Obviously I did not get any signal without an external antenna.

I dont have a car and only cycle to work. But I live minutes away from Wimbledon Common where are large areas of woods (no tall buildings)that i can try my luck in the warmer weather.
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Old 9th Feb 2021, 9:23 am   #8
ex seismic
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

If you want to know what is available to be heard, even if you cannot hear it, use one of the web SDRs.
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Old 9th Feb 2021, 11:04 am   #9
regenfreak
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

Cheers.

Web SDRs take away the electronics side of the antenna hardware which is the fun part.


I am surprised how expensive the commercial telescopic whip is:

https://www.hamradio.co.uk/aerials-a...hz-pd-7829.php

My 5.6m telescopic whip is cheap and it is robust. Probably it is not much different from the expensive one. It is much cheaper to DIY it. At its full extension, the resonance frequency is 13.5MHz with a quarter wavelength of 5.6m. All I need is a DIY loading coil with tappings which can be just a crocodile clip with this calculator to cover frequency below 13.5MHz:

https://www.66pacific.com/calculator...alculator.aspx

Add a PVC pipe extension and a camera tripod, it saves 440.

This web page contains a simple Excel calculator for passive tuned loop design for transmitters. For receivers, it is not necessary to use thick copper pipe to miminize power losses due to skin effect.

http://www.aa5tb.com/loop.html
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Old 9th Feb 2021, 11:43 am   #10
regenfreak
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

I have found a cheap and cheerful solution without spending big money. I have many old studio/portable lighting/camera tripods in storage. This one is portable and ultra stable. It can extend up to 2.5m. So I have a 8.1m telescopic whip that can be taken to the woods in the summer. The giant variometer with ceramic stand0ff was cheap on ebay ( i only paid 9 for it) and its Q can beat the 470 commercial rig's loading coil left, right and centre
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Old 15th Feb 2021, 5:22 pm   #11
JohnBG8JMB
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

Hi Regenfreak
Could you provide a link to the cheap 5.6m whip, please?

73
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Old 15th Feb 2021, 5:55 pm   #12
regenfreak
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

Hi

I paid mime 23 free shipping + 20% VAT on Aliexpress. Mime was shipped from china in 10 days (very well-packed). I ordered from a different seller who no longer sells it:

https://www.aliexpress.com/item/4001118335124.html

Note after Jan 2021, ebay., Aliexpress collect VAT on behalf of UK government and there is no threshold minimum for VAT. Before it was about 14 and now everything is taxable after Brexit.
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Old 15th Feb 2021, 8:04 pm   #13
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Default Re: 5.6m telescopic whip and AUT for SW/Ham receivers

As an alternative, look at the MFJ 1979 - it's 16-feet long and I've in the past used one as a quarter-wave vertical on 14MHz.

[the current Sterling/Dollar exchange rate is getting better, and I recently bought some US gear that was delivered to my door within five days by FedEx, who also dealt with the customs issues]
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Old 15th Feb 2021, 8:58 pm   #14
regenfreak
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Default Re: 5.6m telescopic whip and ATU for SW/Ham receivers

The MFJ 1979 can be purchased at UK around 80 plus shipping:

https://www.hamradio.co.uk/aerials-a...ip-pd-7238.php

I have ordered lots of stuff from USA, the shipping costs are very high. I too got stuff shipped from USA in 4 days last week which is incredible.

The MFJ 1979 is about 45cm shorter than the 5.6m whip. I dont think its build quality is better than the 5.6m whip from China (probably they are all made in china).

For 88 on Aliexpress, you get the whole set with extension poles, loading coils, cable, mount holder and case etc (the whip can extend up to 2.5m):

https://www.aliexpress.com/item/4001...2a542e0eHfv2Bo
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Old 15th Feb 2021, 9:09 pm   #15
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Default Re: 5.6m telescopic whip and ATU for SW/Ham receivers

You can use photographic studio clamp to hold the whip; like this:

https://www.wexphotovideo.com/calume...clamp-1629671/

I have a few of this photographic studio lighting grip heads; they are very strong.

For the DIY loading coil with super high Q, silvered plated wire can be purchased here:

https://www.wires.co.uk/

The above chinese commercial whip kit use stainless steel wire for the loading coil. I dont think it matters that much.

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Old 15th Feb 2021, 10:45 pm   #16
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Default Re: 5.6m telescopic whip and ATU for SW/Ham receivers

For DIY variable loading coil with a slider, these serrated grommet strips are perfect for spaced winding:

https://www.ebay.co.uk/itm/1-0mm-1-6....c101195.m1851

The silver plate wire has transparent insulation to protect against oxidation. A DIY slider would need very low contact resistance to minimise insertion losses.

I found this coil inductance calculator very acurate ( must use average diameter for VHF):

https://m0ukd.com/calculators/air-co...or-calculator/
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