I'm not sure goosing the pull-in voltage is always a good idea. It may
shorten the initial closing time a bit, but (depending on the relay)
it can aggravate contact bounce, doing more harm than good. It also
stresses the relay.
73,
Jim w8zr
Sent from my iPhone
> On Aug 30, 2015, at 10:57 AM, Martin Kratoska <marcom@centrum.cz> wrote:
>
> 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@w8ji.com>
>> To: "Charles Cu nningham" <charlie-cunningham@nc.rr.com>; "'topBand List'"
>> <topband@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
>>> _________________
>>> Topband Reflector Archives - http://www.contesting.com/_topband
>>
>> _________________
>> Topband Reflector Archives - http://www.contesting.com/_topband
>> _________________
>> Topband Reflector Archives - http://www.contesting.com/_topband
>
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|