Hi guys. I just bought a Butternut HF9V9 vertical. I notice it calls for a
length of 75 ohm coax to match - how long should this be?
Tnx

Mogens wrote:

The lenght of the 75 Ohm cable should be an electrical 1/4 wave lenght.
This is free air wave lenght multiplied with the velocity factor of 75 ohm
cable (typical .66).
In meters this should give (300/14.2)*.66 wich should give 3.49 meters.


Hi guys. I just bought a Butternut HF9V9 vertical. I notice it calls for a
length of 75 ohm coax to match - how long should this be?


I'm just curious: how do you figure out a 1/4 wavelength on a nine-band
antenna?

73 .... WA7AA


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Hi Zoran

"Zoran Brlecic" wrote in message
...


I'm just curious: how do you figure out a 1/4 wavelength on a nine-band
antenna?

OK it sounds funny I know. But on 20 meters the HF6/HF9 works as a 3/8
wavelenght antenna, which has a big feedpoint impedance. It would exibit a
high impedance to the tranciever resulting in a high swr.
This is solved by having a piece of 75 Ohms cable which acts as a quater
wave transformer. The resulting impedance is 50 Ohms.
On other bands the 75 Ohm cable has no influence and is also not needed.

Best 73 de OZ1AKN, Mogens

"Mogens" wrote in message
k...
Hi Zoran

"Zoran Brlecic" wrote in message
...


I'm just curious: how do you figure out a 1/4 wavelength on a nine-band
antenna?

OK it sounds funny I know. But on 20 meters the HF6/HF9 works as a 3/8
wavelenght antenna, which has a big feedpoint impedance. It would exibit a
high impedance to the tranciever resulting in a high swr.
This is solved by having a piece of 75 Ohms cable which acts as a quater
wave transformer. The resulting impedance is 50 Ohms.
On other bands the 75 Ohm cable has no influence and is also not needed.

Best 73 de OZ1AKN, Mogens



I dont know about the HF9, but Butternut calls for "RG-11 75 ohm coax,
11'4" if solid dielectric, 13'6" if foam type"

Hope this helps.

This is if the antenna shows high SWR on 20 mtrs, other bands OK.

Kevin