[FARC] Fw: Homemade 3/8 wave 46 mhz vertical antenna RX only - 5 questions

[Jeff Fishman]

Would anyone like to comment on this?
Jeff KB3FIO
----- Original Message ----- 
From: John C.
To: ljfish1 at comcast.net
Sent: Sunday, October 18, 2009 6:42 PM
Subject: Homemade 3/8 wave 46 mhz vertical antenna RX only - 5 questions


Jeff,

Do you know how to answer my questions below? If not, do you know Lou 
Popowsky's e-mail or could you fwd these questions to him?:

Today I bought a RS 102" $19 whip and cut it to 7ft 8 - 11/32in to make it 
into a 3/8 wave for VHF-Low 45.6200 mHz. I used this cutting calculator on 
the web: http://www.csgnetwork.com/antennaevcalc.html. I also used this 
basic design except for that I used a single 1" PVC so only the RS whip is 
used as the antenna and not the pipe:

So far, it seems to work better than my $29 RS rooftop groundplane for some 
freqs I scan but this is on my deck. I've only had a couple of hours to test 
it. These come in loud and clear and include more transmissions than before:

  45.7400 (MD - MontCo WSSC)
  39.400 (MD St Pol)
  46.3800 (VA - Ldn FireDisp)

This works on the ground plane but doesn't come in at all on this 3/8 wave 
but the direction is obstructed by houses and a hill:

  46.4600 (MD - Balt Co Fire/EMSDisp)

This has better voice than the ground plane but has lots of static:

  33.8600 (MD - WashCo-fire)

Distant frequencies have more static than the ground plane but I can hear 
the voice better. Maybe it's because the temporary test location on my 
ground level deck is not grounded yet. I'll take it down tonight & test it 
more another time. The base is 7ft 8in above the ground. Here are my 
questions:

1) Is this concept completely flawed and am I just getting these VHF low 
freqs because it is a long antenna?

2) Does the base height above ground need to be equal to the wave height? In 
this case 3/8 wave is 7' 8" so its base is raised that high.

3) The calculator has these wavelengths as choices: 1/8, 1/4, 3/8, 1/2, 5/8, 
3/4, 7/8, & full. I've only read of 1/4, 1/2, and 5/8 wavelengths...is that 
because those 3 are better?

4) Next, I plan to try a VHF-Hi one for 161 mhz (Railroads) which that 
calculator shows as 5ft. 9 - 25/32in for a full wavelength.

5) Is there a good resource for what I'm specifically trying to do?

Thanks,

John
PS, I'll be out of town on Monday so I won't be able to make to the meeting.




--- On Sat, 10/17/09, Jeff Fishman <ljfish1 at comcast.net> wrote:


From: Jeff Fishman <ljfish1 at comcast.net>
Subject: [FARC] FARC Meeting reminder
To: "FARC reflector" <farc at mailman.qth.net>, "Emcomm" <emcomm at madxra.org>, 
"MADXRA" <madxra at madxra.org>
Date: Saturday, October 17, 2009, 8:07 PM


Just a quick reminder that the Frederick Amateur Radio Club monthly meeting
will be held this Monday, Oct. 19, 7 PM at the Independent Hose Co. Some of
the issues we will be discussing will be the future of the club station,
ways to raise money for the club, and programs and activities for the next
few months.

This month's program will be Joe Durnal NE3R with a presentation on amateur
television.

See you Monday!

73,

Jeff KB3FIO
FARC Pres.

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