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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