Antenna Opinion ?

Thinking of getting an AUSTIN SPECTRA antenna and mounting it on a TRAM 1470 base mount to be as inconspicuous as possible for general scanning..Is this a good combo or are there other better options?

Over the years, I've had several AUSTIN antennas (Spectra, Ferret, and 500) and have never been particularly impressed with their performance. I don't know why they are so expensive.

-John

Radial length matters

Problem with your plan is that it may favor the band which corresponds to the radial length on the mount
and attenuate others. In other words, VHF length radials favor VHF, UHF favor UHF etc. The antenna
may be out of tune on other bands.

If I can find that ARRL/QST articale on radial length and frequency I read in the past (which jives
with my experience), I'll post a link.

regards

KB5UDF->W5JAB

I mounted my Austin Spectra in the rain gutter outside my house on a Larsen NMO mount. Had it on the roof of my old truck before, It excels with VHF/2m. UHF low/70 cm it does decently, UHF high and 800 performance is average. Is it worth the $130 bucks I shelled out for it? Probably not. I give it about 3.5 out of 5 stars

If the OP wants VHF lo band then the Austin Spectra is probably the only currently made scanner antenna that covers lo band plus the other popular bands. The only other choice I know of is the old Antenna Specialists MON series with the micro choke thingee for 800 band.

I did a test between the Austin Spectra, the A/S MON series and a 30 to 512MHz military antenna with some results at the bottom of this thread: https://forums.radioreference.com/scanner-receiver-antennas/264330-austin-spectra.html

The A/S MON series was better at receiving VHF lo plus 2m amateur and 440 amateur out to 470MHz. Above 470 the Spectra pulled ahead and unfortunately I did not measure the 800 band because the article I wrote was mainly about the military antenna that only went to 512MHz.

On the radial length topic, radials cut for the VHF band are usually fine for UHF when the frequency separation is exactly 3X. A 1/4 wavelength radial is a 1/2 wavelength round trip from the feedpoint to the tip of the radial, then back to the feedpoint, which will try and mimic the feed point impedance. At UHF its a 1 1/2 wavelength round trip, which is still a multiple of 1/2 wavelength and will also mimic the feedpoint impedance.

Radials that are shorter or longer than a 1/4 wavelength and result in a round trip length of something other than a multiple of 1/2 wavelength will skew the feedpoint impedance and make it difficult to match. At least that's what the purple antenna Unicorn told me in a dream once......
prcguy

W3JMC said:

I mounted my Austin Spectra in the rain gutter outside my house on a Larsen NMO mount. Had it on the roof of my old truck before, It excels with VHF/2m. UHF low/70 cm it does decently, UHF high and 800 performance is average. Is it worth the $130 bucks I shelled out for it? Probably not. I give it about 3.5 out of 5 stars

Click to expand...

It should work fine.
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The length of the radials need only be 10% longer than a 1\4 wavelength to provide an adequate ground plane so the tram mount provides adequate ground plane for all frequencies above 145 mhz
-
Having longer radials than the minimum needed only makes things better

Old thinking recommend ground radials be 5% longer than resonant and later research shows they should be resonant lengths and not longer.
prcguy

MOTEX said:

It should work fine.
-
The length of the radials need only be 10% longer than a 1\4 wavelength to provide an adequate ground plane so the tram mount provides adequate ground plane for all frequencies above 145 mhz
-
Having longer radials than the minimum needed only makes things better

Click to expand...