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Discussion in 'CB Antennas' started by Wire Weasel, Jul 12, 2019.
Good deal. I like the span you are getting on the SWR also.
YO WW: Well excuse me! The photo does not show the full details of the antenna. Nope got a big screen monitor. The Sigma Venom Silver Rod Antenna looks like the old Hy-Gain Model 579, that uses a impedance marching circuit in its base insulator. Which most of the boys burned out with all their steam. Making Hy-Gain go to the Penetrator advertised to handle 1500 watts. See:
Glad you got it working and your happy with its performance.
Jay in the Great Mojave Desert
If the antenna needs a RF ground to work against and there isn't one built into the antenna or the install then it absolutely will unless you've choked off the feeder.
Assuming it is a length which doesn't present a high impedance on 27MHz.
Without radials to decouple the coax from the feedpoint, the coax will radiate CMC. This is a well known characteristic of an end fed 5/8 wave. If you run little power it may not be any issue but RFI is likely to be a problem at higher power levels.
Hi SW, as has been mentioned, Sigma's math is being questioned. The ant. is exactly 19' - which is a bit longer than 1/2 wave at 27mhz and considerably shorter than typical 5/8 measurements. So it seems it is actually a long 1/2 wave and likely performs more like your Antron 99's etc .... and without the radials. Who knows? All I am reporting is that it is 19.0 feet long and the manufacturer is claiming that it is a 5/8.
That does make more sense since the closer you are to 1/2 wave, the less dependent the antenna is on having radials.
WW would roll the dice right now with conditions. I would leave at 20 ft.at coax. If it's working good enjoy. If not put some radials. Seems there is a small consensus that the mast is your counterpoise.
Hi SW, Are you talking to me or the folks at Sigma? I did not manufacture this antenna
Hi 2315, It's working good and I'm enjoying.
Finally got the 35' push-up pole off the house (thanks to the roofers. I couldn't take it down myself) and now have the Sigma up on top of it in its permanent location on my outbuilding/shack. So bottom of ant. is about 32-33' off the ground and the antenna is working very well. Low noise and great receive. Always choose an all-aluminum over a wire-fiberglass antenna if you can
Wire Weasel I'm curious.
Did your Venom tuneup with the overall length of 19' feet as you stated above, or does it allow to tune by adjusting the top element length a little?
If the kit allows for a little tuning range, do you know what overall length you you ended up with...as measured from the bottom of the mounting bracket to the tip?
Otherwise, if this kit is fixed construction and not tune-able, do you know the frequency where it shows the best resonance?
If the manual shows bandwidth for this antenna, do you know what your antenna shows for <2.00:1 SWR?