[GreenKeys] "Thats a transmitter" (was Collins 709D-1 FSK keyer)

Sun Nov 23 22:48:40 EST 2014

Tony,,

I had to dig up the DX-200 power block manual to refresh my memory and get the numbers right.

Harris doesn't use one very large RF transistor to get to that power level - it uses nearly 2000 of them (and lots of 9-volt batteries).

The DX-200 power block uses 224 power amplifier modules in the power amplifier stage and another 14 power amplifier modules in the driver stage.  Each of these power amplifier modules has 8 IRFP360 MOSFets, I know that is the case with the water cooled modules - I've never seen an air cooled version - it uses a different heatsink on the module, but I'd guess the MOSFets are the same.  Forgive me for not looking at the air cooled manual parts list.

Only kidding about the 9-volt batteries.  The DC voltage for the power amplifier modules is about 250V or so, three phase power from the transformer to a rectifier cabinet adjacent to the power block (in most cases) and there are water cooled SCRs in the rectifier cabinet, well, in the water cooled units, anyway.

The 200kW from each power block goes into a combiner, LC networks, and the output of the combiner feeds the antenna system.  The largest combiner for the DX series, as far as I know, was only a five input unit and that would give 1000 kW output.  To get the 2000kW output, it took the two five input combiners and then the larger two input combiner.

I am not an expert on radar, but yes, the peak power output can be quite high, and with the gain of the antenna system, the effective radiated power of a high power radar is very high.  In radar system, the radiated signal is a pulse, while these MW transmitters are full carrier AM.

73
Sheldon

________________________________________
From: tony.podrasky <tony.podrasky at gmail.com>
Sent: Sunday, November 23, 2014 12:37 AM
To: Sheldon Daitch; Duncan Brown; Nick England
Cc: Greenkeys
Subject: Re: [GreenKeys] "Thats a transmitter" (was Collins 709D-1 FSK keyer)

Hello Sheldon & al;

Sheldon - I'm not very RF-savvy.

Can you explain, please, how you can get such power out of a solid-state
device - and how high is the high voltage in the final amplifier?

I know your post says that it was using a combiner - but I had a friend
that worked on the RADAR on an aircraft carrier - and I don't remember
how much power the RADAR ran - but it was well over a Mega Watt. He said
that they had to remember to turn off the RADAR when they came into
the San Diego base - because each sweep would blank out all the TVs!

73,
ton

On 11/22/2014 11:09 AM, Sheldon Daitch wrote:
> In the high power MW broadcast market, the two biggies were Continental
> and Harris.
>
>
> Harris Broadcast built a few DX-2000 broadcast band transmitters - one
> went to Qatar and another went to Vietnam.
>
>
> I saw the DX-2000, 2000kW output, on the Harris test floor, doing a heat
> run prior to shipping to Qatar.
>
>
> In fairness, the DX-2000 is made of 10 200kW power blocks - five power
> blocks feeding a five input combiner, a second channel of five power
> blocks feeding another combiner and those two combiners fed into another
> combiner for the full 2000kW.
>
>
> All solid state.
>
>
> 73,
>
> Sheldon
>
>
>
> ------------------------------------------------------------------------
> *From:* GreenKeys <greenkeys-bounces at mailman.qth.net> on behalf of
> Duncan Brown <duncanancy at earthlink.net>
> *Sent:* Friday, November 21, 2014 2:15 AM
> *To:* Nick England
> *Cc:* Greenkeys
> *Subject:* Re: [GreenKeys] "Thats a transmitter" (was Collins 709D-1 FSK
> keyer)
> But does it do AM??
>
> Duncan
> K2OEQ
>
> On 20-Nov-14 18:07, Nick England wrote:
>> Heh - that's not a transmitter, THIS is a transmitter...
>> http://www.navy-radio.com/commsta/cutler/naa-qst-3.JPG
>>
>> AN/FRT-31 - 2 megawatts output CW or RTTY feeding 62 miles of antenna
>> wire......
>>
>> Nick K4NYW
>> www.navy-radio.com <http://www.navy-radio.com>
>>
>> On Thu, Nov 20, 2014 at 5:42 PM, Duncan Brown
>> <duncanancy at earthlink.net <mailto:duncanancy at earthlink.net>> wrote:
>>
>>     That's not a transmitter,
>>
>>     _*This is a transmitter:*_ http://www.collinsradio.org/821A/
>>
>>     Collins 821A: 250KW (1000KW PEP) output
>>
>>
>>
>
>
>
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