[BadgerDX]

Hi guys:

I'm a long-time lurker here and by no means an antenna expert. With the transition to ATSC and especially the FCC's desire in the US to further reduce the UHF spectrum available to broadcasters, the noise issues pertaining to VHF-Lo have been clearly articulated here and on other related websites.

I have also had a long-time interest in shortwave and mediumwave broadcasting. I recently came across some literature where H-wave antennas are being promoted as a solution over those frequencies to improve reception that would be otherwise complicated by local noise:

http://www.pixelsatradio.com/PDF/RF_PRO-1A_Cut_sheet.pdf

I also found a reference where H-wave antennas are mentioned as being potentially useful for VHF-Lo (Band I) reception:

http://www.aegis-systems.co.uk/download/ieespectrum3.pdf

You will note that the Pixel literature promotes SNR rather than gain, so I presume the gain of these antennas is not particularly high. That said, if the issue with VHF-Lo is more one of SNR than gain, H-wave antennas might be reasonable. If comparatively small H-wave antennas can be made for MW and HF broadcasting, it makes me wonder if an array of Mobius Loop H-wave antennas for VHF-Lo might be a reasonable size, thereby providing modest gain at high SNR.

What do you Think?

BadgerDX

 

[morehp]

To me it looks like you are basically buying an extremely good preamp.... one that injects very little noise. So you can take an antenna that has low gain and amplify the weak signal without adding noise...

wonder what one of these quality preamps would do to the performance of some of the DIY antenna on this site ... like say the stealth hawk. or even the large double gh ... it might make for a great extreme fringe signal catcher combination....

 

[300ohm]

Their literature is somewhat confusing. The output from their antenna to the preamp is coax.
However, in their backup documentation showing a moibus strip loop here on page 12 figure 4 (pdf page 13):

http://www.ece.unm.edu/summa/notes/SSN/note7.pdf

a moibus strip loop is designed as two coax lines that terminate into a twinax output.

being promoted as a solution over those frequencies to improve reception that would be otherwise complicated by local noise:

Well, the old tried and true fix for that is to locate the local noise problem and eliminate it. Generally in most cases, thats easier than trying to filter it out, heh.

 

[holl_ands]

The various UHF and Hi-VHF Loop Antenna designs I've analyzed thus far are BROADBAND
"resonant" loops, where the diameter is about one wavelength:
http://www.imageevent.com/holl_ands/loops

SMALL Loop Antennas operate quite differently and are typically NARROWBAND. Note that
the suppression of LOCALLY generated noise ONLY applies to sources in the NEAR-FIELD,
which is less that a wavelength from the antenna [That's under 17-feet for Ch2. SORRY!!!!!].
They are more suited for suppressing noise coming from within your home in the HF band,
where the "near field" is much larger:
http://www.w8ji.com/magnetic_receiving_loops.htm [Loop WORSE than Dipole, except when VERY CLOSE]
http://www.aa5tb.com/loop.html [Lots of info re Small Loop Antennas]
http://www.vlf.it/octoloop/rlt-n4ywk.htm [Simplified Loop Antenna Theory & Calculations]
http://www.66pacific.com/calculators/small_tx_loop_calc.aspx [Small Loop On-Line Calculator - TRY IT!!!!]
http://sidstation.loudet.org/antenna-theory-en.xhtml [Small Loop Antenna Loop Theory]
http://sidstation.loudet.org/antenna-noise-en.xhtml [Small Loop Int/Ext SNR Calculation]

 

[BadgerDX]

H-Field Practicality

Holl_ands:

Thanks for your thoughts and the links. It's clear that an H-Field antenna is not a cure-all for the problems on VHF-Lo.

 

[Jase88]

That's an expensive solution! $399? Wow....

I see this antenna also covers up to 30MHz, which is far below channels 2-6. And while I realize that you're merely using this model as a demonstration of what could be possible for VHF-LO, I'm not sure that it's workable. In fact, I don't believe this antenna would work well for reducing noise/interference at 30MHz and below--where signal propagation off the ionosphere occurs regularly. It's difficult to filter noise and interference coming at you locally and from thousands of miles away.

As mentioned, determining the source of the interference may be more productive. Eliminate your own home first (do the breaker test).

If you have aerial electrical lines in your area, and the problem disappears during high-humidity or precipitation, it's likely those lines causing the problem.

Does the interference look like herringbone patterns? It may then be FM interference. Note that most pre-amps--if equipped with an "FM Trap"--only offer about 20dB or less of FM frequency attenuation, which is often inadequate.