Topband: skirt-feed vs short gamma feed

[n4is]

'>>My question for the group is:  If I choose to use the de-tuning
skirt for a transmit feed system instead of the short gamma rod system can I
expect to see any improvement in my transmit signal?  <<

Hi Gary

I'm using a UNIPOLE over 5 years and I can answer your question.

1- The UNIPOLE is very broadband if the antenna length is around 100 degree.
The impedance will be close to 200 ohms and you can tune it using a 4:1
balun and a single series capacitor. Using a L or T network makes the
antenna even more broadband, My is 1:1.0 on 1.8, flat from 1.825 to 1.855,
1:1.2 on 1900 and 1:1.5 on 2 MHz.

2- On 80 m the thing is different; I was not able to find a way to tune the
tower and get a broadband SWR may be because it is too long.

3- You will need two different capacitors to tune the skirt on 160m and 80m.
You can tune it for min noise onto the RX antenna system. Also will be
necessary another relay for TX/RX disconnecting he skirt from the coax or
antenna tuner.

4- You won't be able to connect the gamma match together with the skirt, I
did this and the gamma match detuned the skirt, however you can add a relay
to use them separated.

5- The high impedance does not mean better performance; your signal will be
the same with both configurations.

6- The Skirt is easy to tune using a jumper to the tower and a relay for
each band. There is a point where you can jump to the tower and get 50 ohms
or 200 ohms and tune with a single series capacitor. N7OP wrote a nice
article on ARRL Antenna compendium #7, "Untangling the Folded Unipole". It
is a very good project with the shorting stubs for 160/80/40m


Regards
JCarlos
N4IS