Happy accident getting the VHF/UHF array together.

[KJ3N]

Started work on getting the rooftop tripod back up and the VHF+ antennas back in the air. The final array will have 6m, 2m, 70cm, and 23cm. The 144, 432, and 1296 antennas will be fed into the IC-910H, and the 6m antenna goes into the RCS-10, to be fed to the K3.

I had purchased a used Icom AG-25 for the 2m port of the 910 a couple of years ago, but since I haven't had a 2 m beam up for close to 4 years, I never checked it out. My bad.

It appears that there's something wrong with it. When engaged, it raises the noise floor from s0 (actually more like -3) to s7. Not a good sign. From what I've been able to tell, this is usually an indication that the FET may be bad.

So, I dig up the old Mirage KP-2/144 that I had taken down several years ago. I thought I was going to retire this thing in favor of the AG-25, because it would have worked seamlessly with the 910. Now, I figure I'm going to have to deal with additional cabling to get the control box for the Mirage integrated into the setup.

The Mirage is setup for RF switching by default. There's a separate input on the control box for PTT control, but I'm not looking forward to doing all this additional wiring in the first place. I barely have enough time to get the antennas up before this weekend's VHF contest. I don't need additional headaches.

Then it dawns on me. The 910 sends 12VDC up the coax to the AG-25. The control box for the KP-2/144 does the same thing. If I simply sub the Mirage for the Icom preamp, this should work. A few minutes changing cables and, lo & behold, it works. The Mirage gives me a noise floor of about s1-2, which should be enough RX amplification to make the 910 not so deaf.

Looks like a KP-2/440 may be in my future as well. It's certainly more affordable that most other RX preamps on the market. It's a shame they don't make one for 1296. The prices on those are enough to give you a heart attack.

[N8YX]

I'm probably going to do the same thing, with a twist: Remote three amplifiers (6/2/430) somewhere outside of the radio room. Then run control lines for their remotes along with extension cables for the SW-200 sampling heads back into the operating position.

One could get tricky with the concept and build a set of MUXed transceivers using a Stamp, Arduino or similar microcontroller at each end of the circuit. Three channels of A/D and D/A along with nine channels of amp control (three each Opr, SSB/FM, Pre On) could be sent back and forth between stations in the form of a 9600 baud data stream. For those extremely long runs, one could utilize optical fiber transmission to reduce interference potential.

Oh, the possibilities...

[KJ3N]

I'm probably going to do the same thing, with a twist: Remote three amplifiers (6/2/430) somewhere outside of the radio room. Then run control lines for their remotes along with extension cables for the SW-200 sampling heads back into the operating position.

I could see running remote amps for 432 and 1296. Not sure I see the point in doing it for 6m and 2m, unless you had some REALLY long runs of cable.


One could get tricky with the concept and build a set of MUXed transceivers using a Stamp, Arduino or similar microcontroller at each end of the circuit. Three channels of A/D and D/A along with nine channels of amp control (three each Opr, SSB/FM, Pre On) could be sent back and forth between stations in the form of a 9600 baud data stream. For those extremely long runs, one could utilize optical fiber transmission to reduce interference potential.

That's way more work than I'd ever plan to do. I like the idea of being on the higher bands, but I'm not going to get that gung-ho about it.

[KJ3N]

Ok, day 2 is over and all the antennas are up, coax and hardline are run, and nearly all the outdoor work is done. Just got to put a few clamps on the 7/8 hardline where it runs down one of the tripod legs.

Did find out a couple of interesting things, however. Seems my BCB filter (which I keep in line to deal with potential 160m issues from the AM station about a mile away) doesn't pass 50 MHz worth a damn. The Nye Viking SWR/power is also not liking 6m, either.

I had checked the 6m beam before I put it up to make sure it was alright. It had a near perfect match from 50 to 51.5 MHz. When I got into the shack and did a final check, I had a 2:1 SWR. Couldn't figure it out at first, so I started bypassing anything that might be a problem. The easiest item to start with was the BCB since it's right along the side of the operating position. That brought the SWR down to around 1.3:1. When I removed the Nye Viking meter, everything was near perfect on 6m again.

Lesson learned. Guess I'd better pull out the Diamond CN-101 and get that in line instead. Not sure how I'm going to deal with the BCB filter issue yet, but it's coming out of line for this weekend.

[N8YX]

Did find out a couple of interesting things, however. Seems my BCB filter (which I keep in line to deal with potential 160m issues from the AM station about a mile away) doesn't pass 50 MHz worth a damn.

Not sure how I'm going to deal with the BCB filter issue yet, but it's coming out of line for this weekend.
What are it's pass/stop-band characteristics?

[KJ3N]

What are it's pass/stop-band characteristics?

Exactly what the label says, if I had bothered to read it in the first place. :doh:

1.8-30 Mhz. :oops:

[KJ3N]

So everything is now complete. Cut the hardline to length, put the female connector on, and installed the 1 foot jumper between the 910 and the hardline. I am now fully functional on 6m, 2m, 70cm, and 23cm.

Here are the results of 3 days worth of work.

9786

I can copy the VHF/UHF beacons out of Philly on all available bands. http://w3ccx.com/techinal.htm#Anchor-BEACON-11481

Signal strength on 2m and 70cm is very good. S9 or better on both, with the 70cm beacon about S9+10. No preamp on the 432 antenna yet. I'll add that later.

The 6m beacon is only about S6, but the K3 is known for needing a little help on this band, plus it's all groundwave propagation. Maybe I'll spring for the PR-6 some day.

The 1296 beacon doesn't seem to get much above an S3. Most of the time it barely gives any signal strength at all, but it never fades away completely. Given that I've got about 2db loss between the 25 feet of 9913 and 50 feet of 7/8 hardline, the antenna is 15-20 feet below the tree line, and I don't have a preamp for that band, I'm actually pretty happy. It will be interesting to see if I make any contacts on the this band with only 10W out of the 910. I figure I'm getting about 6-7W to the antenna. Amp and preamp are long down the road for this band.

I'm going to be aching for the next few days..... :fever:

[KG4NEL]

Wish there was someone to talk to above 6M on SSB around here :(

Used to be a regular 2M SSB net, but I believe it was winding down when I got my license in '01.

[KJ3N]

Wish there was someone to talk to above 6M on SSB around here :(

Used to be a regular 2M SSB net, but I believe it was winding down when I got my license in '01.

Interesting that you should say that.

I was chatting with a local ham last night while checking out the setup. He commented that he's seen a significant drop off on VHF/UHF activity over the last several years. He blames it on the Extra being so easy to get that everyone is moving to HF. Now all the activity that he hears is strictly contest related.

YMMV

[WØTKX]

Start a group like we have here... activity almost every night.

http://www.rmvhf.org/wordpress/

[KJ3N]

Start a group like we have here... activity almost every night.

http://www.rmvhf.org/wordpress/

Already have one. It's been around for 57 years. http://www.w3ccx.com/

Activity nets every Monday night. http://www.w3ccx.com/airtimes.htm

I've just never remember to check them out.

Also, this is the first time in at least 3 years that I've had antennas up for 6 & 2. I've never had antennas up for 432 or 1296.

[N8YX]

Point your antennas towards Ohio on Sunday morning...then listen for the weekly 6M net on 50.125 around 9AM-10AM.

[KJ3N]

Well, it's all over for the June VHF contest. Kind of a disappointment overall. There were no real openings to be had on any band. There was one very brief opening on 6m to the West. I also caught a weird 5 minute opening into Canada on 2m. I ran into a few people who commented that this was not one of the better June contests. Everybody was apparently scraping for contacts.

Found out the Mirage preamp has some sort of thermal problem. After baking in the sun, and powered up for 5-10 minutes, it starts injecting tons of garbage into the 2m RX. Not good. The up side of this problem is that I found out that the AG-25 preamp does actually work. Seems that there's an adjustment on it that if it is not set correctly, will give you bad S/N, which is the problem I was having. I also found out that the S7 noise I was getting with it on, is more a function of where I'm pointing the antennas. If I'm pointed towards the West, I only have about an S2-3 noise level with the AG-25 on. This is more inline with what I expected. Now, I have to swap the preamps around, which won't happen for a few days.

Another issue that reared its head is what happens when the Cushcraft 719B gets wet. The antenna is spec'd at 430-450. Apparently, this is when it's bone dry. When it gets wet, the SWR raises noticeably below 432.600. This, of course, upset the IC-910H. The result was I had reduced power until the antenna dried out some time around 10 this morning. I'm already contemplating a replacement antenna. Probably the M2 440-21ATV, which is spec'd at 420-440. It also has 2 more elements than the 719B.

Other lessons learned:

A preamp on 432 is an absolute must. While I did make 17 Qs in 8 different grids, it was very hard to hear anyone who wasn't within 30-40 miles. Not going to make that mistake again. Also, the additional gain would help in being able to more accurately aim the beam. On the contacts that were further out, it didn't take much to lose them if the beam wasn't nearly dead on them to begin with. I did, however, make a couple of 120+ mile contacts on 432, even though none of the UHF antennas are above the tree line.

1296 Mhz during the summer is a bear, especially if you're below the tree line. I made 2 Qs, which is more than I actually thought I'd do. One was only 18 miles; the other 34 miles. Again, I had no preamp for this band, which I'm sure didn't help. Looking around at SSB Electronics' web page, I'm not ready to hand over $500 for a 1296 preamp, so that's a problem I'll have to live with for a while. Maybe the January contest will yield better results on 1296 with all the leaves off the trees.

Final breakdown:

6M = 30 Qs and 12 grids
2M = 33 Qs and 12 grids
70cm = 17 Qs and 8 grids
23cm = 2 Qs and 1 grid

Furthest contacts:

6M = 1,136 miles
2M = 356 miles
70cm = 222 miles
23cm = 34 miles

[WØTKX]

http://www.ve1alq.com/preamps/preamps.htm

[KJ3N]

http://www.ve1alq.com/preamps/preamps.htm

Interesting, but unless I missed something (at this hour that's possible), I don't see any RF switching relay. Any mast mounted preamp I'm going to use has to be able to handle 20-40 watts being passed through it.

[X-Rated]

I should be a rover. I live near a gridsquare corner. One morning last week on my way to work, I drove through EN51, then EN52 to pick up a calibrated capacitance meter, then through EN62 and finally EN61 where I work. EN62 has really a small amount of land in it. Millions of people though.

[KJ3N]

Any mast mounted preamp I'm going to use has to be able to handle 20-40 watts being passed through it.

Looks like I may have found a solution. Advanced Receiver Research has 2 lines of RF switching preamps. One line handles 25 watts, while the other handles 160 watts. The 25 watts model is $190 and the 160 watt model is $240. Very affordable, compared to the $500 that SSB Electronics wants for theirs.

Although they don't specifically list a 1296 preamp, on their Special Frequency page they suggest that a custom preamp can be had at no additional charge. http://www.advancedreceiver.com/page12.html

I still need a 70cm preamp, so I may just order the 160 watt model for 432 and the 25 watt model for 1296.

[KG4NEL]

Yep, I gave the ARR line a hard look when I was still looking to build a 2m/440 omni array for satellites.

Now that all the interesting ones have asploded or are about to, that project is on hold for a while...