Tom, Are you saying that it is not possible to decouple with a coaxial sleeve such as is commonly used on VHF or UHF collinear antennas ? It was used for many years quite successfully as a quarter wa
coaxial sleeve ? No. It doesn't decouple well but it decouples. It decouples because the coax inside the sleeve is 1/4 wl long electrically. This creates a high impedance effectively in series with
Other approaches are careful design of the transmission line inside the bottom half of the dipole. The usual run of the mill UHF/VHF antenna isn't loaded, and so, getting the coax to be 1/4 wave lon
There are often unnoticed assumptions buried in VHF antenna design extrapolated to HF. In the sleeve antenna, the relationship of the sleeve to the coax is mechanically controlled. The generous separ
Finally, the justification I need for the building permit review board!... I have to have that 1000 ft tower, or my feedline won't be adequately decoupled, and there might be RFI. I'm just trying to
practicalities at objections. Actually it is pretty well known among antenna engineers that the decoupling isn't very good. The fact decoupling isn't good is what gives rise to the coaxial skirt col
Hey, while we are on the subject, how about gamma matched yagis. I have a friend who swears by using a gamma match on his yagis with no feedline choke. Seems to me that this is a great way to add som
When I had a gamma matched Wilson 20M yagi, the common mode voltage on the coax was so high the coax actually arced between the tower leg and the coax shield. I was only using a 4-1000A amplifier, s
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I have a Cushcraft X-7 which is not a pure LPDA but uses a log cell. It is fed thru a 4:1 balun and I route the coax along and taped over the boom (the tx line is below the boom). Except on 10m where
I don't think the Cushcraft has a "hot boom". I think it has insulated elements. You wouldn't tape your coax to the balanced feed wires of the Cushcraft would you? Some manufacturers tell people to t
LPDA mfrs excited booms and it recommended to LPDA's elements lieu of this, which line to an LPDA? to cut it for most WB2WIK/6 Assuming a 50 ohm feed: If you run the coax along the hot boom, just ru
My guess is that, for your location, your chief concern with a 1000 foot tower would be right-of-way access for guy points. Close behind in second place would be FCC/FAA approval. <smile> [snip] Fina
Yes, I suspect you are right, Tom. It will be interesting to see if changing the feed to one with better balance will make our 10 meter antenna any quieter. Too bad its stacked above two other big ya
You don't understand.. the 1000 foot tower (300 meters, actually) is to hold up my HDTV over the air antenna so I can receive signals from Mt. Wilson (some 20 mi to the East). There just happens to b
Strange. I´ve used gamma matched yagis for 35 years or so and also used (at times) very high power, never had a failure or any problem with it. Sure a gamma match isn´t a perfectly balanc
I never really noticed a pattern problem, but then how do you A-B test between a gamma and a balanced feed? I noticed a voltage (and thus current) on the shield problem. Power levels and cable lengt
practicalities at objections. Actually it is pretty well known among antenna engineers that the decoupling isn't very good. The fact decoupling isn't good is what gives rise to the coaxial skirt coll