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 New 23cm amp, RF switching dilemma 
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Post New 23cm amp, RF switching dilemma
Just arrived today new 23cm amplifier, built by W6PQL Jim over in the States, rated at 10w in for over 150w out, data report with the amp shows around 185w output with 10w in so quite a good amount of power for 1296 Mhz, just put my smaller version ( single PA device ) on ebay to fund this one, anyway I'm wondering the best way to run this for SSB ( mainly going to be used on ATV so no need to switch from RX to TX there ) would the best route be 2 seperate antennas & switch manually at radio end with switch unit, or invest in good quality RF switching relays, never used them before so not really got much knowledge of usage, any ideas anyone, thanks Tony.

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Fri Jul 16, 2010 2:58 pm
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 New 23cm amp, RF switching dilemma 
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Post Re: New 23cm amp, RF switching dilemma
You'll need two coaxial relays. An o/p relay handling 200W @ 1.3GHz is not cheap.

Suggest a CX-230 on the input and a CX-520D on the output (o/p).

Of course if you're not using hardline such as LDF4-50 or LDF5-50 to the antenna then you might as well chuck it all in the bin
and just use the smaller PA (you've just flogged) at masthead.

Better solution is to fit it all at masthead, inc. switching, on the antenna.


Fri Jul 16, 2010 7:33 pm
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 New 23cm amp, RF switching dilemma 
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Post Re: New 23cm amp, RF switching dilemma
Thanks for the reply Dave, the coax system is being upgraded very soon, as you say decent relays that can handle high power at 23cm dont come cheap, but thats the cost of playing at higher UHF, loved your monthly articles in PW by the way, always the first section I browsed after it dropped through letterbox, cheers...................Tony M0ATV


Fri Jul 16, 2010 8:51 pm
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 New 23cm amp, RF switching dilemma 
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Post Re: New 23cm amp, RF switching dilemma
g4asr wrote:
You'll need two coaxial relays. An o/p relay handling 200W @ 1.3GHz is not cheap.

Suggest a CX-230 on the input and a CX-520D on the output (o/p).

Of course if you're not using hardline such as LDF4-50 or LDF5-50 to the antenna then you might as well chuck it all in the bin
and just use the smaller PA (you've just flogged) at masthead.

Better solution is to fit it all at masthead, inc. switching, on the antenna.

Not a lot I can add to that. :D
I'd go for the masthead mounting option.
The CX-520D isolation http://www.caelectrocomps.co.uk/cx520d.htm isn't all that good so i use Radiall R570012035 relays http://radiall.applixia.net/catalogue/object.do?action=datasheet&object=2635445 on 23cm and on the 13cm project.

With a masthead pre amp you could go for a lesser coax on the RX path and, on the TX path it depends on how much drive yo have at the bottom end.
If you only just have enough to drive the amp then the lowest possible loss, remember there will be, at least, 0.25 Db loss in each of the relays.
If you have more than enough drive then you can afford to loose some in the run to the amp.
This assumes it is at the masthead.

If the amp is in the shack then, obviously, as low a loss, and as high a grade as possible.

The dielectric in some coaxes does very unfortunate things in the presence of high levels of 23cm.

What is the operating voltage/current for that amp?
I'll have to go and look at the site.
Have you run it into a dummy load yet?

Don't forget to sequence the changeover.
Probably no need to say that but is there? :)

I look forward to a cracking signal off you shortly. :D

Just been to the sit.
I quite like the 600W version. :D
Just about enough output for in the shack use.

Cheers

Tony

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Fri Jul 16, 2010 9:30 pm
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 New 23cm amp, RF switching dilemma 
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Post Re: New 23cm amp, RF switching dilemma
Hi Tony, thanks for the info, yes I believe some coax dielctrics find 23cm high power a bit too much to handle, heres a pic from PE3ATV who ran 500w at 23cm into RG-213 for a while, ouch !!

Image

check out PE1RKI's amp page, he has some fantastic amps especially for 13cm very tidy milling indeed for some of the watercooled ones

http://members.chello.nl/b.modderman/index2.html


the amp I have here runs off 24-28 v DC & draws around 10 amps at max output, power supply arrived at 7.30am this morning from Hong Kong, I have a smaller amp which can give 10w out to drive the bigger amp, thats for ATV use of course, for SSB my TS-2000x will deliver the 10w out direct, looking forward to trying it this weekend.............Tony


Sat Jul 17, 2010 8:16 am
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 New 23cm amp, RF switching dilemma 
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Post Re: New 23cm amp, RF switching dilemma
I've seen that photo before :shock: and had first hand experience of what can happen with dodgy, or the wrong choice, of coax. :D

Some very nice machine work on PE1RKIs site. :)

I'll be on 4M on Sunday but will keep an eye on 23cm after the contest.

I'm looking for a 50W, or so, amp for portable but, ideally, it needs to be 12V or I'll have to build a 12V to 28V converter.

Cheers

Tony

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Sat Jul 17, 2010 9:58 am
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Post Re: New 23cm amp, RF switching dilemma
I've put my smaller single PA amp on ebay last week, runs out tonight, rated at up to 5w in for 87w out but again needs to be 24-28v DC I know you can buy 12v to 24v up converters but not sure how ell they work, seen them on ebay a couple of times, here's my old amp nearly gone > :)

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... :MESELX:IT


Sat Jul 17, 2010 10:06 am
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 New 23cm amp, RF switching dilemma 
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Post Re: New 23cm amp, RF switching dilemma
Hi do you have seperate output and rx ports if so all you need is one relay connected to the amp output and the swithed side to the aerial thats the way i did it on 23 cm if there seperate put amp in the tx line and connect rx to otherside stright through then all you need to do is switch after the amp and all will work ok if any problems email me your number and i will ring you as long as its not a mobile phone but if you only have one port in and out then you will need to relays amphenol relays can be picked up second hand quite cheap and will handle kw hope this helps


Tue Jul 20, 2010 5:30 am
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 New 23cm amp, RF switching dilemma 
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Post Re: New 23cm amp, RF switching dilemma
g7igc wrote:
amphenol relays can be picked up second hand quite cheap and will handle kw hope this helps

I'd be pleased to be pointed at any relays which will handle 1kw , at 23cm, with good insertion loss, SWR and isolation figures.
What is the model number.
At the moment I'm using the Radiall R570012035. I was fortunate enough to get four for less than £200. :)
I've not seen any that cheap since.
You must not forget to sequence the system so it is not possible for RF to be present before the relay has fully changed over.

With the amp taking 10amps there should be no problem with running it at the mast head with the resultant extra output. :D

Hopefully you will be on for tonights UHF UKAC.

Cheers

Tony

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Tue Jul 20, 2010 8:45 am
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Post Re: New 23cm amp, RF switching dilemma
Hi Phil, I only have one port available for TX on main amp, the driver amp has 2 ports, radio I was going to be using ( if at all, as amp was purchased for primary ATV use ) was TS-2000x, will reply in detail later, just rushing out at moment, thanks a lot for help.


Tue Jul 20, 2010 9:37 am
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