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

[Steve Rodgers]

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




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

[Steve Rodgers]

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
>
>
>




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

[Bob Dengler]

At 5/5/2005 09:58 PM, you wrote:
>Steve:
>
>As a matter of fact, I do have tuneup instructions that I got from
>Microwave Associates.
>They are attached.

"Initial tuning of this unit must be done at power levels of 10 watts or 
less.  Severe damage can result to untuned units by the application of 
power in excess of this limit."

I can see a TX being damaged by excessive reflected power from an untuned 
isolator's input, but damage to the isolator?

Reason I bring this up is because when I tune an isolator with a TX, I put 
another (already tuned) isolator between the TX & the isolator being tuned 
to make sure the latter sees 50 ohms on all ports.  So I don't have to 
worry about what the TX sees because it's already isolated, but I also run 
~30 watts or so to get a good indication on the Bird using a 50 watt slug.

Bob NO6B






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

[Micheal Salem]

Steve:

You are welcome.ÂÂ 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.ÂÂ 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





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

[Micheal Salem]

Bob Dengler wrote:

  
"Initial tuning of this unit must be done at power levels of 10 watts or 
less.  Severe damage can result to untuned units by the application of 
power in excess of this limit."

I can see a TX being damaged by excessive reflected power from an untuned 
isolator's input, but damage to the isolator?

  

Bob:  

I think that they may be concerned about off resonance circulating 
currents or voltages during tuneup which could demagnetize (or 
change the permanent fields of the internal magnets and damage 
the isolator. 

I would have to look it up, but I think that this isolator takes 
up to at least 100 watts.  That would be when it is in resonance. 
I have run 65 watts through it with not much trouble. 

Micheal Salem 





  
  















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

[Kevin Custer]

Micheal Salem wrote:

>As a matter of fact, They are attached.
>

I have uploaded the 7R011 Tuning Instructions to RBTIP.  Maybe Mike 
Morris would be so kind to add a link or index so folks can find them.





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

[Kevin Custer]

Thanks go out to Mike Salem for providing the information.  I forgot to 
say that in my post with the link.


Thanks Mike,
Kevin

Micheal Salem wrote:

>As a matter of fact, I do have tuneup instructions that I got from Microwave 
>Associates.
>  
>




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

[Micheal Salem]

Skip:

I did look it up when I got home in my ancient M/A-COM 
catalog (From 1982, no less.  It is hard to throw this stuff 
away). 

For those who are interested, the 7R011 is specified 
at 125 watts.  The insertion loss is .9 db typical with 
1.3 db max.  The isolation can be as high as 60 
db with 50 db typical.  That may require breaking out 
the HP435B and an RF head to tune it.  But I could get 
a good null right down to zero indication at 10 watts in 
and a 1 watt Bird element on the output and  expected 
that I had at least 40 db or more of isolation.  It is 
described as a metro style isolator.

The 44004 load that comes with the typical IM 
panel that includes the 7R011 is rated at 100 watts 
and I would agree with Skipp that it would not be a 
good idea to dump more than 100 watts through the 
device.  With 125 watts in and an insertion loss of 
.9 db. there probably isn't more than 100 watts 
in the dummy load, but you could be dissipating 
a lot of power in heat in the isolator in an open 
antenna condition.

Micheal Salem N5MS
Norman, Oklahoma 



skipp025 wrote:

  
I would have to look it up, but I think that 
this isolator takes up to at least 100 watts.  
That would be when it is in resonance.
I have run 65 watts through it with not 
much trouble.
Micheal Salem


  
  
The port loads are under sized if you want real 
protection.  The units operate just fine at 100 
watts fwd power... at least that's what Motorola 
had been blowing through them for some decades. 

As long as the antenna system works as it should, 
the loads are probably ok for lower power levels. 

But I wouldn't trust the supplied port loads as 
a failsafe. 

skipp 



  















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

[Mike Morris WA6ILQ]

At 06:36 PM 5/6/05, you wrote:

>Micheal Salem wrote:
>
> >As a matter of fact, They are attached.
> >
>
>I have uploaded the 7R011 Tuning Instructions to RBTIP.  Maybe Mike
>Morris would be so kind to add a link or index so folks can find them.
>

The information is more topic-oriented to the antenna systems page,
so it's now there.
See 
under "Isolators and Circulators".

The permanent home of the actual document is at
.

Mike WA6ILQ





 
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