Topband: KD9SV-OK1RR relays ???

Martin Kratoska marcom at centrum.cz
Sun Aug 30 12:57:06 EDT 2015


It is here:

http://www.somis.org/

73,
Martin, OK1RR

Dne 30.8.2015 v 16:32 Larry napsal(a):
> Measures (K6???) did a relay speed-up scheme for QSK on an SB220, I
> don't remember the details but it was something like hitting the relay
> with higher than usual coil voltage/current and it shortened up the
> relay pull-in time. It might be more complicated in this application
> than needed. I don't have the URL to Measures' site but it can probably
> be found by a search.
>
> 73, Larry  W6NWS
> -----Original Message----- From: Douglas Ruz (CO8DM)
> Sent: Sunday, August 30, 2015 8:41 AM
> To: Tom W8JI ; Charles Cu nningham ; 'topBand List'
> Subject: Re: Topband: KD9SV-OK1RR relays ???
>
> Tom and all members of the list thanks for your ideas and time !!!!.
>
> I have a plan B:
>
> I added a BNC female connector in the rear panel of my old Yaesu, FT747 (It
> is an FT80C, the commercial version with metallic chassis) few months ago.
>
> I was using that BNC to feed an SDR receiver using the same antenna.
>
> If i add a SPDT switch also on the rear panel and RE-WIRE the BNC
> connection
> i can get an RX port in my old radio and can connect an RX antenna...like
> modern radios...Switch Pos A (main antenna at SO239)...Pos B (SO239 for TX
> and BNC for RX)...i made few mods to my radio, so, i know it very well...
>
> Maybe that will help...of course, i must add then an Front End
> Saver...still
> need a fast relay !!!
>
> Maybe the Plan A with a 5mS relay will be more easy...still need a fast
> relay too !!!
>
> 73....Douglas, CO8DM
>
> "No creo que haya alguna emoción más intensa para un inventor que ver
> alguna
> de sus creaciones funcionando. Esa emoción hace que uno se olvide de comer,
> de dormir, de todo." - Nikola Tesla
> ----- Original Message ----- From: "Tom W8JI" <w8ji at w8ji.com>
> To: "Charles Cu nningham" <charlie-cunningham at nc.rr.com>; "'topBand List'"
> <topband at contesting.com>
> Sent: Sunday, August 30, 2015 12:27 AM
> Subject: Re: Topband: KD9SV-OK1RR relays ???
>
>
>>> It seems to me that a very fast operating preamp protection circuit
>>> could be
>>> constructed employing a good fast saturating NPN switching transistor
>>> across
>>> the antenna path. In receive mode the collector-base junction would have
>>> substantial reverse bias and the transistor can be chosen for low
>>> collector-base capacitance. With a fast switch like a 2N708 or something
>>> similar the switching time will, of course, FAR outperform a relay
>>> closure
>>> time.
>>
>>
>> This thread might have splintered. I was responding to this:
>>
>> <<Your FT-747 only has one antenna input. It does not have a second
>> <<receiver. It doesn't even have a receive-only antenna input. You cannot
>> <<transmit and receive at same time. Why do you need a "front end saver"?
>>
>>
>> If it is a transceiver without an RX antenna point, the problem is
>> adding a receive antenna to a transceiver that does not have a receive
>> port.
>>
>> If it is a transceiver with an RX port, the requirement for an
>> external "front end saver" and what will work depends on the antennas,
>> the power, the transceiver, and the antenna spacing.
>>
>> A front end saver can be very simple with some radios, more
>> complicated, or not needed at all.
>>
>> An external switch is never easy to do correctly, unless the radio has
>> good TX RX switching time sequencing.
>>
>> I'm unclear what the application is, but a 10 mS relay is really too
>> slow for either application. The sequencing issues I pointed out apply
>> to both systems.
>>
>> 73 Tom
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