Re: [Repeater-Builder] Looking for Microwave Associates 7R011T Isolator Tuning Procedure

[Micheal Salem]

Steve: You are welcome. Maybe Kevin or Mike will post it to the website. Let me make a couple of points that I hope will help. I learned these many years ago when I had a 7R011 given to me. Someone had tried to put a PL-259 into the N connector and sheared off the interior pin. I took the 7R011 apart and was able to fit a new female chassis N connector on the isolator. I could never get it anywhere near the specs. So, I called Microwave Associates and spoke to someone in their repair department. I described what had happened and what I had done. He told me that this was very tricky to do and that they used nonmagnetic copper vises to position the isolator just right when assemblying or repairing it. For not much money at the time (maybe $50.00 to $70.00, I don't remember), they repaired the connector and it came back like new. I also got some information from the repair man about the isolator and how to treat it. He told me to be sure and use brass or other nonmagnetic materials when mounting it and to not to take it off the panel. It mounts on the panel on standoffs. So brass screws and aluminum standoffs were what I used. All I got was the isolator (that was all that was broken). But a friend of mine had an aluminum panel that he had for one. I eventually acquired a couple of the low pass filter around and at Dayton one year and had a couple of the 100 watt Microwave Associates dummy loads that it took and a smaller 25 watt load. It tuned up and seemed to work well. I ran it on a UHF repeater with no problems. One of the problems in tuning was getting enough sensitivity to read the reverse hookup (RF into the antenna port and measure power coming out of the transmitter port). I had a 1 watt UHF slug, so that I could read .1 watt and that could be about 30 db from 10 watts. However, it occurs to me that you could use that W7ZOI wattmeter that uses the Analog Devices RF power measurement chip (I think AD8037)) which would let you use lower power and go down -50 to 80 db. Might want to put a 20 db attenuator in line in case you get it out of tune and a lot of power comes down and blows up your Wattmeter. Of course, I think that Microwave Associates was expecting everybody to have an HP 435B with an appropriate RF head is what they are looking at, but the Gilbert Cell AD8037 seems to me to be a good replacement. I recently got another 7R011 and will have to dig out an aluminum panel to put it on and get some dummy loads. I hope this is helpful. Micheal Salem N5MS Norman, Oklahoma Steve Rodgers wrote: Michael, Thanks, This is exactly what I was looking for. Steve WA6ZFT On Thursday 05 May 2005 21:58, Micheal Salem wrote: Steve: As a matter of fact, I do have tuneup instructions that I got from Microwave Associates. They are attached. I have successfully tuned a 7R011 using these. I did not have a power meters, but could use a smaller element in a Bird wattmeter and got pretty good isolation. Micheal Salem N5MS Steve Rodgers wrote: Does anyone have a tuning procedure they could share for the Microwave Associates 7R011T dual-stage UHF Isolator? I have 2 of these tuned on 454 and 462MHz. I've never attempted to tune isolators so any tips would be useful. Can these be tuned with a tracking generator/spectrum analyzer? Steve WA6ZFT Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/ Yahoo! Groups Links To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/   To unsubscribe from this group, send an email to: [EMAIL PROTECTED]   Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.