The 6 meter 53.030/29.6 repeater project
Or, a 6m Repeaterwith a 10m remote base...
This repeater project is an effort to put a little life into 6 meter FM in this area and to take advantage of the many low band mobiles that have entered the surplus market at very low prices.The planned location for the repeater is a 200 foot tower nearby to the 400 foot tower the 443.100 is located on. It is a small scale tower similar to a Rohn45G tower. It is located on a ridgeline of what passes for mountains around Abilene.
Originally we planed on using 2 GE Low Band Rangr89 radios and a UHF GE Rangr89 for a remote base and link control. At the Midland Hamfest, WX5TX, John, gave us a GE Master II shelf unit, with the continous duty PA. Although the cards were for a 37mhz base and can't really be easily converted, KD5TKR has obtained a GE Master II mobile that is currently on 49mhz, complete with ICOMS. We have moved the cards from the mobile unit to the base/repeater shelf WX5TX provided. Clearly, the GE master II will make a superior 6 meter repeater. Gary, NZ5V has recently obtained some 49mhz Master II 2C ICOMS, so the repeater shelf is complete.
Charles has also donated a Micor 330w low band base, and if the duplexers will support it, the new repeater will sport a 330w output, to balance these 100w mobile radios we are using. Ok, I know, but remember that our homebrew duplexers will nock that 330w down to about 225w.
The Antenna - Click here to see the antenna portion of this project.
The 6m Duplexers - Click here to see the duplexer portion of this project.
At this time we have ordered the crystals for the 2c channel elements, they have come in and are installed and working nicely. The GE Mastr II receiver is tuned up, however the exciter does not seem to want to tune up on 53.030 at all. Off for some Mastr II expert help at this time from W5MUH or KC5OZY.
UPDATE 8-26-04 Thanks to Rogers, W5MUH, the MastrII is now producing 105w on 53.030. It's been turned down to 75w just to be safe.
We had planned to use a software controller from the same people who wrote the EchoLink software. But as luck would have it, the kit built NHRC controller never worked, and a Zetron controller came our way at a VERY good price.
Getting the GE MasterII station to operate on 6m as a repeater has been an adventure. Tweaking both the exciter and the receiver to full factory spec's took at least two trips through the tune-up process for each.
Then there was the mis-advendure of the noise blanker. Forgetting comments made in the GE Yahoo group a long time ago, I left the noise blanker operational on the receiver, and of, course, operating as a duplex station, the noise blanker received all the duplexer noise that was present and made the receiver somewhat hard of hearing. The answer is to either leave the noise blanker disconnected or to attach it to a separate antenna far from the repeater's.
I also found that the GE tone board was not a very good choice. Receiver sensitivity with the PL board installed was a lot lower than without it. Presently it is not being used, and the repeater is operating without PL, and using the controller's internal squelch.
A second controller, a four relay DTMF board wil provide control over the 29.6mhz remote base transceiver, a GE Rangr 16channel, 100w unit, and a single DB grounded folded dipole near the top of the 200' tower. The remote base link radio's frequency can be contolled via a second DTMF controller with a 1 of 4 latched output to choose the channel on the remote base. By using this DTMF controller, we can control the remote base 10m radio. It can be changed to one of the 16 preprogrammed simplex or repeater pairs using a 6 meter radio with a touchtone microphone.
The Completed 6m Repeater
The repeater was completed in June of 2005, after a long, long time, and a lot of hard work by many people. To give a rundown on the spec's... while an HP 8754A network analyzer was used to build the duplexers, the proof is in how well it works!
|Transmitter power output = 97w||Transmitter power out to antenna = 72w||1.29db Insertion loss per measurements|
|Receiver sensitivity at Rcvr port =0 .26uv||Receiver sensitivity at antenna = 0.35uv||1.57db insertion loss per measurements|
|Equipment used:||Motorola||M2550A Service Monitor|
|Hewlett Packard||8754A Network Analyzer|
The controller used in the final installation is a Zetron 45B, which provides the usual repeater control functions plus 4 sense lines, plus 3 control lines that are all available for remote control via DTMF.
A Little History on Low Band
When I picked up the MastrII shelf from W5MUH, Rogers, he told me some very interesting stories about DB Products and the antennas Joe, KD5YCY gave me for this project. Seems the antennas were from the Schlumberger low band site that was located on the Potosi Tower many years ago.
Rogers reported that the old low band repeater really had some range... much better than VHF or UHF - so, Rogers, we are looking forward to getting this one on the air.
We hope that this 6 meter repeater, given such a good location, should have excellent coverage. The 443.100 UHF repeater has about a 60-75 mile usable radius of coverage from 400ft AGL. We hope that 6 meters will provide a 75 to 100 mile radius of coverage from this location using 100w commercial radios.