I had problems with a copper J-pole, also. I had copied the design from
the ARRL handbook. Unfortunately the dimensions of the fittings in the
book were not the same as the ones that I assembled it with. Ron, above,
mentions the dimensions. After I researched the dimensions I had to
unsolder
First, is the SWR meter rated for UHF? Are you measuring at the antenna or end
of feedline. Make sure when you make a measurement, it is in open air, no other
objects nearby, UHF is affected by other objects. Are you using an antenna
analyzer or SWR meter? Best to use a Bird meter with UHF
A VNA would answer all of these questions.
G.
On 4/21/2020 3:45 PM, Rick Hiller via BVARC wrote:
1.9 :1 across the whole band? Is actual z lower or higher than 50
ohms? Is it resonant where you wish or somewhere else?
GL. Rick. RH
Sent from my i-Thingamajig
On Apr 21, 2020, at 3:23
Ralph,
First, check you dimensions. The calculated dimensions are:
Radiator (Long) = 19.44 inches (I would cut to 19.75 and trim down to
bring the resonance up
Stub (short) = 6.48 inches (I would cut 6.5 ")
Feed point = A touch less than 5/8 inch FROM THE TOP ( not the middle) of
the bridge on
1.9 :1 across the whole band? Is actual z lower or higher than 50 ohms? Is
it resonant where you wish or somewhere else?
GL. Rick. RH
Sent from my i-Thingamajig
> On Apr 21, 2020, at 3:23 PM, SETX Telecom via BVARC wrote:
>
> Not enough to make a difference...did you adjust the
Ralph:
No, any reasonably conductive metal will have a free space
velocity factor of 1.0. However, putting conductive objects
very near to a metal wire or tube or rod will change this.
Also, any insulation on a wire will reduce the velocity factor.
I just bought a nanoVNA-F vector network
Not enough to make a difference...did you adjust the matching? It can
vary...just like a gamma match, etc..
On Tue, Apr 21, 2020, 2:52 PM ralph phillips via BVARC
wrote:
> Having problems with my home brew 440 mhm jpole...will not tune better
> than a SWR 1.9. Books and articles no help. Will
Having problems with my home brew 440 mhm jpole...will not tune better than a
SWR 1.9. Books and articles no help. Will velocity factor or resistance
change dimensions for steel vs aluminum??
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