On 03/21/2014 07:54 AM, Jon Danniken wrote:
Ralph Mowery wrote:

Ok on the vertical dipole. For this antenna you need to run the feedline
horizontal from it for a couple of feet and then down.

The impedance of this antenna should be around 70 ohms and if I were you , I
would use some 70 ohm rg-6 coax back to the receiver.

The 300:75 converter is actually a balun that has a 4 to 1 ratio. It
normally does 2 things, changes a 300 ohm to 75 ohm inpedance such as many
TV antennaas were set for 300 ohms so the twin lead could be used. As
things changed over the years, the newer TV sets had a 70 ohm input for the
coax cable. The 300:70 could be used either way, 300 ohm antenna to coax or
coax to the old 300 ohm input of the TV.

Removing it from the vertical dipole (70 ohm inpedance) and using coax to
the receiver will probably help.


Thanks Ralph, I'll try that this weekend and see what the results are (I
have scads of RG6).

Well, I got up on the roof and reconfigured the antenna today, and got a
nice improvement from my setup. Unfortunately I wasn't very scientific
about figuring out what made the big difference, but I did remove the
4:1 balun and ran the coax out horizonally for ~1/4 wavelength. I also
soldered the old crimp connection at the base of the elements; they were
reading about six ohms from the twinlead to the tips before, now the
resistance is low enough to not be measured by my DMM.

After the work today, noise is down ~10dB, and I can make out a lot more
transmissions, with much higher clarity, than I could before. I still
occasionally get a transmission with a strong signal that sounds
garbled, but everything else is coming in very nicely.

Thanks for the suggestions, they paid off.

Jon