Years ago I lived in a house that was forty feet above the Chesapeake Bay. Three yagi antennas, covering 2m, 70cm, and 23cm, pointed towards New England. At a height of ten to twenty feet above the ground, there were no obstructions for the first several miles. Stations in New Jersey, Connecticut, Rhode Island, New York, and further, were regularly worked.
Fast forward to today, I’m now living in a house that is completely surrounded by trees. Putting up an antenna suitable for terrestrial UHF and SHF communication definitely requires a tower of suitable height. Also, being able to use more bands is also desired. This is going to require more planning than what I did for the previous installation.
Plan A
My initial thought was to purchase an Icom IC-905 transceiver. This new radio supports many of the VHF, UHF, and SHF bands. The benefit of this radio is that the transceiver is tower mounted, meaning that your feed line can be much shorter than having to run multiple lines from the ground. This is both a cost savings and a signal savings.
I read a review of the IC-905 written by Terry Price, W8ZN. Honestly, it doesn’t sound like a bad deal. I’d still need to figure out 1.25m and 33cm but that’s okay if everything else is going to just work.
I drew up a spreadsheet to determine what the effective radiated power (ERP) would be for each band and then compared it to doing the same thing from the ground using existing radios. The numbers were a little surprising but not completely unexpected.
| Transceiver | Frequency (MHz) | Power Out (W) | Power Out (dBm) | Connector Loss (dB) | Feed line Length (ft) | Feed line Loss (dB) | Antenna Gain (dBd) | ERP (dBm) | ERP (W) |
|---|---|---|---|---|---|---|---|---|---|
Icom IC-905 |
144 |
10 |
40 |
8 |
0.129 |
12.6 |
52.5 |
176,644 |
|
TBD |
220 |
25 |
44 |
8 |
0.161 |
14 |
57.8 |
605,118 |
|
Icom IC-905 |
432 |
10 |
40 |
8 |
0.227 |
16.5 |
56.3 |
423,936 |
|
TBD |
902 |
25 |
44 |
8 |
0.335 |
20.5 |
64.1 |
2,596,809 |
|
Icom IC-905 |
1296 |
10 |
40 |
2 |
0.102 |
21 |
60.9 |
1,229,702 |
|
Icom IC-905 |
2400 |
2 |
33 |
2 |
0.143 |
23.4 |
56.3 |
423,380 |
|
Icom IC-905 |
5600 |
2 |
33 |
2 |
0.232 |
32.8 |
1,896 |
||
Icom IC-905 |
10000 |
0.5 |
27 |
2 |
27.0 |
500 |
|||
TS-2000X |
144 |
100 |
50 |
108 |
1.699 |
12.6 |
60.9 |
1,230,552 |
|
TS-2000X |
432 |
50 |
47 |
108 |
2.971 |
16.5 |
60.5 |
1,126,860 |
|
TS-2000X |
1296 |
10 |
40 |
108 |
2.975 |
21 |
58.0 |
634,600 |
What I learned was that for 2m and 70cm, using the IC-905 would be actually worse than feeding the antennas from the ground! This is mostly due to the feed line not creating so much loss due to the lower frequencies involved. The other factor is the transmitter on the ground has more output power. Comparing the 23cm options is more equal and shows where the Icom IC-905 will shine. Microwave bands will also be better coming from the IC-905, although the radio only supports 13cm, 5cm, and 3cm (leaving out 9cm).
Then I wrote to Paul, WA3QPX, asking for his opinion. This is where things kind of went off the rails (in a good way).
Plan B
Paul told me about a five band transverter from Q5 Signal. The transverter covers all amateur bands from 2m through 23cm so I wouldn’t have to figure out 1.25m and 33cm and the receive is supposed to be real good. Discussions on the Down East Microwave website suggests they are in the process of developing a microwave transverter that will cover 13cm through 3cm. My new thought is to use these devices and maybe start with the VHF and UHF bands, adding the microwave bands when that new transverter becomes available.
Now I need to figure out if I can tower-mount the Q5 transverter in an effort to reduce feed line cost and loss.
Tower and Antennas
I’ve got ~80 feet of Rohn 45 tower in the yard that needs to be sandblasted, repaired, and repainted. I also have a set of azimuth and elevation rotators. If I mount all the antennas to a frame (see below) I could rotate all the antennas vertically, allowing for EME and satellite work. I’ve never tried EME but would be willing to give it a shot.