Construction of an active rx only hula-loop antenna

Useful information regarding antennas for SDR products.
Paul
Posts: 236
Joined: Fri Feb 17, 2017 9:52 am

Construction of an active rx only hula-loop antenna

Postby Paul » Thu Jan 11, 2018 5:43 pm

Great litlle video by Kevin Loughlin
Link: https://www.youtube.com/watch?v=EDRPzoNoFhc&t=206s

Appeared attractive - so, out with "junk box" and about an hour after finding the bits, my bodge-up was up and running.
It's only a small (24") kiddies hoop, but DOES actually work up in an attic room (as high as I could get it) with or without amplification.
With amplification and tuning supplied via an old (externally powered) Vectronics AT100 atu/amplifier and connected via a 3-way switching block to the RSP-2 Port B, it is performing perhaps surprisingly well from at least 2 Mhz to 14 Mhz and I also did a quick vhf check, that showed it capable of receiving local FM radio and packet transmissions (which might be handy for someone just setting up and proving their RSP at very low cost indeed).

Reason: No reason

g1hbe
Posts: 350
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: Construction of an active rx only hula-loop antenna

Postby g1hbe » Fri Jan 12, 2018 12:16 am

I find loops fascinating and extremely useful from a noise-busting point of view. I have a Wellbrook loop type 1530 and it has saved my hobby from the curse of noise. However, as you say it is is quite possible to make a loop for very little cost if you use a little ingenuity. I have built a number of active loops with 'bargain shop' hula hoops, usually measuring about 3 feet across. A plastic conduit junction box makes a good housing for the active electronics at the base. The amplifier I use most is basically similar to the PA1M design and it works well. The HF response is not as good as the Wellbrook, but as my main interest is LF/MW and the lower HF bands this does not matter. I have found that two or three turns is better for VLF signals at the expense of a droop at the higher frequencies.

Reason: No reason
Andy

Paul
Posts: 236
Joined: Fri Feb 17, 2017 9:52 am

Re: Construction of an active rx only hula-loop antenna

Postby Paul » Fri Jan 12, 2018 12:49 pm

Thanks for the observations Andy, with regard to loop size and multiple turns etc.
I had considered increasing the number of turns and had actually already ordered a 36" loop (as an aside, I had no idea how difficult it might prove to source a "simple" hoop as they now seem fashionable exercise devices).
Of course, having scented success, I am becoming more ambitious and would be grateful for any advice on offer, such as whether simple household lighting wire that I am currently using, or whether 1.5mm earth wire or perhaps light-weight speaker flex might offer an improvement.
Although the antennas that I have outdoors are serving me pretty well for general vlf/mf/v/uhf, I did fancy an indoor option and this seems to be just the job.
As an aside, you did offer me some really useful useful advice with regard to reception of ndb's, which I am successfully receiving via an Ukrainian made active mini-whip on Port A of an RSP2, which of course has the vhf/mf filter.
I can see how their pursuit might become addictive - there's always something to look for.....
Unfortunately, I doubt that I'll get a Wellbrook past my "financial adviser" just yet, but at least I've got "my feet wet."

Reason: No reason

duggae
Posts: 2
Joined: Wed Jan 10, 2018 3:22 pm

Re: Construction of an active rx only hula-loop antenna

Postby duggae » Wed Jan 17, 2018 4:50 pm

I built a 36” rx loop several years ago. Used 3/8” copper tubing (the soft bendable variety). A smaller 12” loop of 8 ga copper wire was supported inside the large loop and tuned with a 365 pf variable cap. The contraption was held together on a broomstick. You can find plans on the www. It was very effective on BC and lower. Gave it away a while back but I’m gonna build another today. I have a wide range ten tec preamp to ply with also. We’ll see how it works.
Last edited by duggae on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason

Paul
Posts: 236
Joined: Fri Feb 17, 2017 9:52 am

Re: Construction of an active rx only hula-loop antenna

Postby Paul » Wed Jan 17, 2018 6:00 pm

Hope this new essay into home-brewing works well for you.
I'm just on to my unambitious Mk2 version - now a 36" hula-hoop (one turn of twin-core lightweight electrical flex - fed through a so-called
active antenna by Vectronics (had it for some years and little used until now) - ait's n ATU with control over gain.
Pretty pleased with the results so far- from 3Mhz to 15 Mhz, comparing favourably with my outdoor antennae.
For some reason that's not clear to me, whilst really good over the range, the 8Mhz band is pretty bad - maybe local maybe transitory, but the other antennae don't share the problem.
Mk 3 will be a little later,,,

Reason: No reason


Return to “SDR Antennas”

Who is online

Users browsing this forum: No registered users and 1 guest