Michael,
Thanks for the additional info. The "soft" power meter on the HP8920 service
monitor goes down to 4 decimal places
maybe this will be useful for low power testing.
Steve
WA6ZFT
>
> From: Micheal Salem <[EMAIL PROTECTED]>
> Date: 2005/05/06 Fri PM 01:59:44 EDT
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Looking for Microwave Associates 7R011T
> Isolator
> Tuning Procedure
>
> 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
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
>
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/
