Fwd: Re: [Amps] IC-718 and AL-811: Icom manual misleading, interface necessary according to Icom technician

[Will Matney]

Yes, there is a spike, but one can control that by putting a diode across
the relays coil or a zener diode across the collector and emitter of the
transistor, just a shade higher than the operating voltage. When a spike
develops, it's clamped. A switching transisor for this could be isolated
also, in that it's emitter would only go to an insulated jack on the
transceiver. This way it would only see the relay coil. However, I like
the relay better as it should be used if a higher current rating is
needed. Evidently, that relay in question is a weakling.

Best,

Will


On Fri, 4 Feb 2005 15:52:03 -0500, Bolbach, Timothy <TBolbach at ssoe.com>
wrote:

> Will,
> 	By using a relay the switching currents and voltage spikes
> encountered when completing the inductive amplifier relay circuit is
> isolated from the transceiver ground plane.  Also, the circuit minimizes
> a path back into the transceiver for RF feedback.  By using a transistor
> output, the transistor would have to be referenced to the transceiver
> ground. Unless, of course, it is opto isolated, well.... that's a
> different story.  - KD8CN = Tim
>
> -----Original Message-----
> From: Will Matney [mailto:craxd1 at ezwv.com]
> Sent: Friday, February 04, 2005 3:21 PM
> To: Amps at contesting.com
> Subject: Re: [Amps] IC-718 and AL-811: Icom manual misleading,interface
> necessary according to Icom technician
>
>
> I believe if it were me, and I were building transceivers, that I would
>
> make sure it would switch everything out there, including the oldies.
> That
> just sounds like an awful small amount of switching power either way it
>
> goes. Ameritron says its at 100 mA on their switching, and that actually
>
> may be a little high as I imagine it switching a 12 Vdc DPDT 10 amp
> contact relay. I know using either a 2N2222A or even a 2N3904 will
> switch
> those with no overloading of the transistor, they run as cool as a
> cucumber. If that little relay is that small, I would have just used one
>
> of those transistors in it's place, switching to ground. I think, if I
> recall, Rich Measures has a schematic on his website for converting some
>
> of the old amps to low voltage, low current, switching. See, to me, I
> dont
> think an end user ought to have to do this, it ought to be there to
> begin
> with in the transceiver. I'll almost bet that what they pay for that
> little relay is more than the cost of the transistors!
>
> Best,
>
> Will
>
>
>
> On Fri, 04 Feb 2005 12:08:02 -0800, <gdaught6 at stanford.edu> wrote:
>
>> Hi Will,
>>
>>> I wonder if you got a reply from someone that dont know what they're
>>> talking about by the sounds of it. Heck, a small 2N2222A will switch
>>> the  load there with room to spare.
>>
>> The transistor switch is what I use:  I simply installed one in my
>> amplifier, so it pretty much doesn't care what the source of the T/R
>> switch signal is.
>>
>>> Surely, they dont have the
>>> switching coming  straight off an IC? I dont have a schematic of it
>>> here to look at and see  what they've done, but that just dont sound
>>> right. Also, if it has an  actual internal relay, even a small reed
>>> type at that, it sould switch  that amount.
>>
>> No, it's not an IC, it's a small relay.  My (contesting) experience
>> was that the contacts would begin to stick, even when switching well
>> within their specified voltage & current.
>>
>>> When they said "either" 16
>>> volts or 2 amps, but not both, is  a bunch of hogwash. It just sounds
>
>>> to me like a ploy to get around  warranty work no matter what!
>>
>> I don't know.  I've had nothing but good experiences with Icom.  But
>> the T/R switch output is way happier seeing my 0.6v @ 2ma load than it
>
>> was seeing my 12V relay.
>>
>> 73,
>>
>>  George T. Daughters, K6GT
>>
>>
>>
>>
>> __________ NOD32 1.880 (20040928) Information __________
>>
>> This message was checked by NOD32 antivirus system.
>> http://www.nod32.com
>>
>>
>
>
>



-- 
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/