[hpsdr] Advantages/Disadvantages of Pin diode switching?

[Sid Boyce]

Very interesting Kjell.
I have used PIN diodes at the 10W level and I have had a number of 400W 
PIN diodes around that I have not used to date.

Apart from a review of a commercial unit with circuit but no component 
details in QST going a long way back I have not seen any other references.

Are there any references to circuit details you could recommend?

The use of 1N5408's sound an interesting alternative. I also have a 
number of back-to-back High power Schottky diodes on old power supply 
boards.
73 ... Sid.

On 03/06/13 08:34, Kjell Karlsen wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi John.
>
> I see you mention Apollo in your mail. The first version had bot as 
> options but the result with the diode switch is so good that the 
> layout with a relay was dropped.
>
> The signal loss in a diode switch is a bit higher than in a relay, 
> around 0,5-1 dB. That is both in TX and RX.
>
> By the way, it seems as there is no need to use PIN diodes, 1N7000 
> variants works as well at this power level. S1M is used by Elecraft 
> for RX path and 1N5408 in the TX path in their 500W PA! But at this 
> power level, you must use high voltage to block for the RF, at 10 W, 
> 12 V is enough.
>
> And if you are a CW man, the QSK is fantastic!
>
> 73, Kjell
>
>
>
> På Mon, 03 Jun 2013 08:07:53 +0200, skrev John Marvin 
> <jm-hpsdr at themarvins.org>:
>
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> I've modified my hermes enclosure to prepare it to support a qrp amp. 
>> What I've done is add 3 different boards (all mounted to the inside 
>> bottom of my Hammond enclosure): 1) The Hardrock 50 driver amp 
>> (available separately as a kit for $35 from HobbyPCB -- used to boost 
>> the 0.5W Hermes output to 5W), 2) A small 5V keying circuit for the 
>> driver amp (the driver amp requires 5V to key it, which is normally 
>> provided from the Hardrock 50 amp board,  and 3) a T/R relay board 
>> based on Gerd's Antenna Switch design.
>>
>> I split 2 and 3 above into separate breadboards since I'm not sure 
>> what my final T/R switch solution will be, and I'll probably replace 
>> the T/R board with either a better T/R relay board or a pin diode 
>> switching board. After doing some research, my first choice amp is 
>> the Elecraft KXPA100, which is not yet available. One of its features 
>> is pin diode switching. I would lose the benefit of that as long as I 
>> am using a T/R relay to drive the amp. After doing some research, I'm 
>> not clear on why it appears that some people prefer relay switching 
>> to pin diode switching. I understand that there are some limitations 
>> for high power cases, but Elecraft seems to think it is an advantage 
>> for their 100W amp. So I'm wondering why 1) Apollo has both choices, 
>> 2) it appears prototype designs of the Hardrock50 used pin diode 
>> switching, but the final design uses a T/R relay, and 3) most amps 
>> that could use pin diode switching do not us it.
>>
>> There must be some disadvantages in using pin diode switching, but I 
>> haven't found a discussion that points them out. I wouldn't think it 
>> would cost significantly more. Are there some issues with reliability 
>> or signal loss?
>>
>> Thanks,
>>
>> John
>> AC0ZG
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>


-- 
Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
Senior Staff Specialist, Cricket Coach
Microsoft Windows Free Zone - Linux used for all Computing Tasks


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