I use a 17ft whip for bands 6m - 20m meters. I can use 12 8ft radials or I
can use a 4x8 faraday cloth. Either of these give me a 1.2 or lower SWR.
When I add a shorty 40 coil for either 30m or 40 meter, I need to add three
33ft radial to either the 12 8ft radials or the faraday cloth to give 1.2 - 1.5
on 30m, 40m and 60m. On 75m my SWR jumps to just under 2.0. My GUESS is
just the 12 8ft radials or just the faraday clath does not give the required
ground area needed for 40m or higher. I have yet to try the 12 radials, and
farady cloth. Will try that this week end.
The above is not based on any rule or math, just what I have found with my set
up and the readings I have taken.
Rudy Ackerman KF5QYG
On Tuesday, June 18, 2024 at 02:39:31 PM PDT, Andre Pollard via BVARC
<bvarc@bvarc.org> wrote:
I normally use a 5’x8’ faraday cloth which works fine on 20 and up. I made up
16 radials 10 feet long to try that and saw no difference.
On Jun 18, 2024, at 4:24 PM, wb5itt <wb5...@att.net> wrote:
What kind of a ground system do you have?
Chris WB5ITT
Sent via my Samsung Galaxy S10e, an AT&T 5G Evolution capable smartphone..so
there! 😂
-------- Original message --------From: Andre Pollard via BVARC
<bvarc@bvarc.org> Date: 6/18/24 4:19 PM (GMT-06:00) To: BRAZOS VALLEY AMATEUR
RADIO CLUB <bvarc@bvarc.org> Cc: Andre Pollard <apollard...@gmail.com> Subject:
[BVARC] Antenna help
I need one of our antenna gurus to give me some input-
I have an 18'-4" telescoping antenna I have been using when camping. By
adjusting length, I can get it to tune at <1.5 SWR on all bands 20M and above.
So far so good, but when do we ever leave well enough alone.
I'm getting ready to travel for a while, and wanted to extend the range down to
40M. So I used the calculators at Coil-Shortened Vertical Antenna Calculator
(66pacific.com) to determine the necessary coil. It said I need 4.9 mH. I made
the coil per the calcs one the same site, using a 1.9 inch diameter PVC pipe.
I'm running it bottom-loaded.
By tapping the coil a couple of turns down, I can get it to tune to 7.2 mhz,
but the SWR is >6. If I put my hand very close to the coil , the frequency
shifts (expected), and the SWR drops to 1.2. So I tried adjusting the length
and tapping different turns, never better than 4 SWR on any frequency around 7
mhz. However, if I get my hand near the coil, SWR drops.
Thinking this meant I needed capacitance, I tried a hat to the whip, with
several different designs and sizes. Changes frequency, but horrible SWR still.
Bypassing the coil I can adjust the whip and get great SWR on 14 mhz and above.
So, I don't think it's a problem with the coax (20 feet of RG8X) or nanoVNA.
Google shows up all sorts of sites showing making a coil loaded shortened
vertical like i'm trying. None mention the issue I'm seeing as a problem.
I'd appreciate any input, I've been 'learning' on this for a couple of days now
and haven't gotten it to work yet.
Thanks,AndreW4SFZ________________________________________________
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