Can someone tell me what the extremes are on typical t/r relays in amps? Many
newer amps seem fine with a 10ms delay from keydown to RF. I'm wondering if
there
are amps that are even quicker than this and what some worse case scenarios are
with older amps.
Thanks!
-------------------------
73,
Greg - AB7R
Whidbey Island WA
NA-065
On Wed Apr 2 6:50 , John/K4WJ sent:
>I use a DEO QSK-1500 for my QSK operations. This is a PIN diode unit
>that K8RR and W4TV designed back in the 80s. It was rather expensive
>in those days but there are a few of them out there that can be
>purchased in the $150 to $200 range. I have two QSK-1500 units, but
>one needs repair.
>
>
>I've discovered that some of the sellers are elderly and have abused
>their units to the point that some repair is necessary. However, they
>are very easy to trouble shoot and can be repaired rather cheaply
>unless the main transmit PIN is damaged. Then it becomes a rather
>huge task trying to locate one of these PINs. (It is rare for them to
>be damaged.)
>
>I did a poor job of matching my antennas to the transmission line so
>I use a TenTec 238 to bring the SWR down to a level that doesn't
>bother the QSK-1500. I use the QSK-1500 with a TenTec Omni VI Plus
>and either a Ameritron ALS-600 or an old Alpha 77, which is currently
>on the fritz.
>
>One plus for using PIN diodes is that they are silent.
>
>I have no idea what Alex is talking about when he mentions that they
>operate as a noise diode. I can't tell the difference in the received
>signal between having the QSK-1500 in the transmission path or
>by-passed. I can copy the weakest DX signals. However, I've never
>taken any noise measurements with the unit in or out of the receive
>path, I'm only going by what my ears tell me.
>
>I LOVE my QSK-1500s.
>
>73..de John/K4WJ
>
>
>At 02:41 AM 4/2/2008, Alex wrote:
>>Hi guys:
>>It so happens that during the last 2 years or so I worked on high power
>>amplifiers in the kilowatt range .
>>PIN diodes are made by very few manufacturers, coming and going all the
>>time. They can run In the 300$ dollars range, are susceptible to burn out at
>>mediocre SWR,s and require back bias voltage approximately 3 times the PTP
>>RF voltage involved. They also require a forward current of a few hundreds
>>of mA to conduct well when open. This adds directly to the input noise
>>because they operate as a noise diode would.
>>In short, if you don't need fast switching speeds, don't mess with them.
>>They also have only a poor isolation of around 30 dB. In QRO use the
>>leftover power at the receiver port is still to much so that you need some
>>additional switching after the main diode with associated driving circuits.
>>In short, drop it!!!
>>73 and all the best:
>>Alex 4Z5KS
>>
>>-----Original Message-----
>>From: amps-bounces@contesting.com
>>[amps-bounces@contesting.com','','','')">amps-
bounces@contesting.com] On
>>Behalf Of Kim Elmore
>>Sent: Wednesday, April 02, 2008 4:48 AM
>>To: amps
>>Subject: Re: [Amps] Relays
>>
>>Thanks, Vic! Makes perfect sense. Yes, the PIN diodes are quite
>>expensive, especially for ones capable of handling much power.
>>
>>73,
>>
>>Kim N5OP
>>At 06:28 PM 4/1/2008, you wrote:
>> >Kim Elmore wrote:
>> >
>> > > But, this does lead to a question: are PIN diodes avoided simply
>> > > because using them is far more complex than relays, or is there some
>> > > other reason they aren't often used?
>> >
>> >The cost of the diodes and associated circuitry is more than a cheap
>> >relay. And they are susceptible to damage from lightning-created
>>transients.
>> >
>> >I had an Alpha 86 with pin-diode switching that worked great. Never any
>> >problems. But a lot of Alpha users did have problems and at some point
>> >they started using vacuum relays. Someone who can afford a newer Alpha
>> >can tell us if they still do!
>> >--
>> >73,
>> >Vic, K2VCO
>> >Fresno CA
>> >http://www.qsl.net/k2vco
>> >_______________________________________________
>> >Amps mailing list
>> >Amps@contesting.com
>> >http://lists.contesting.com/mailman/listinfo/amps
>>
>>_______________________________________________
>>Amps mailing list
>>Amps@contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
>>
>>_______________________________________________
>>Amps mailing list
>>Amps@contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
>
>73..de John/K4WJ
>ex K8PXG 18 Jun 1959 to 11 Feb 1997
>K8WJ 12 Feb 1997 to 08 Apr 1997
>
>
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|