With all of this, I still have concerns that the HA-14 amp will be "hot
keyed"...... noisy relay or not. Hot keying an amp is rough on the amp
relays and other components in the amp. I think this application would be
best served by a PTT circuit for CW.
I strongly urge one to use the "keying loop" provided by the Tentec Omni VI
Plus system. Although it requires different and additional circuitry within
the amp, it allows the switching to take place before RF is generated by the
transceiver and subsequently applied to the amp thus the amp T/R relay has
switched and settled. Of course should the amp not provide QSK capability,
then one should not try to operate QSK modes.
73
Bob, K4TAX
----- Original Message -----
From: "Paul Christensen" <w9ac@arrl.net>
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Sent: Tuesday, December 11, 2007 8:05 PM
Subject: Re: [TenTec] OMNI VII QSK users with good ears....
>> "Well, i have a Heath HA-14 and i have an isolation relay between the rig
> and the amplifier. The relay in the amplifier is quite noisy, however
> when i'm not using the amp, the relay in the rig seems to be quite loud.
> Since i have the isolation relay at the power supply to the amplifier, i
> was thinking of maybe using a 4N33 optoisolator to replace the relay in
> the rig, but was thinking that maybe someone else has come up with
> something better."
>
> You should avoid using an opto-isolator by itself as the sole keying
> mechanism to the amp. The opto-isolator should be used as the interface
> between the rig's internal key line and a robust switching device like a
> MOSFET.
>
> If I was to go into an Omni Six again, here is the tack I would take: To
> simplify the job, I would use the Jackson Harbor Press "Key All." This is
> a
> small PCB with an opto-isolator feeding a pair of high-voltage,
> high-current
> MOSFET transistors. You can construct your own, but this product provides
> a
> very clean installation whereby the PCB can be affixed to the side wall of
> the rig with 3M double-sided tape. The Key-All is USD $15.00 and includes
> shipping CONUS.
>
> http://home.att.net/~jacksonharbor/keyall.htm
>
> I no longer have an Omni Six manual so perhaps others can apply the
> schematic numbers to what I am describing from memory:
>
> 1) Lift one of the base biasing resistor going to the small TO-92 style
> transistor. The transistor is used as a current driver for the noisy amp
> keying relay. This will prevent the relay from becoming active if you
> forget to disable it from the rig's menu. If you're careful about leaving
> the relay disabled in the menu, this step can be bypassed. Still, I would
> lift the transistor biasing resistor. The lifted end can be soldered back
> down again if you ever decide to sell the Omni six;
>
> 2) Find the "T" voltage buss on the Omni Six schematic. It appears at
> several locations on the Control Board. Find the buss, and connect one
> side
> of the key-All input (R1) to the "T" buss. The other Key-All input lead
> of
> goes to the Omni's circuit ground. R1 on the Key-All is the
> opto-isolator's
> LED current limiting resistor. The 120-ohm value should be fine, but I
> would probably ensure it is valued correctly so that roughly 17 mA flows
> through the LED from the "T" voltage source (+5VDC I believe). That said,
> I
> would verify the "T" voltage with a DVM. If it is higher than +5VDC, R1
> needs to be increased accordingly to maintain roughly 17 mA through the
> opto-isolator's LED (Ohm's Law still works in 2007);
>
> 3) Ideally, the Key-All's MOSFET pair should remain floating above ground
> for use with AC-switched amp key lines. What I am not sure of is whether
> or
> not the Ext. AMP RCA connector on the Omni Six's rear panel can isolated
> above ground. If it can't, then you may be limited to amps with only a DC
> key line.
>
> As an alternative, the "T" voltage could be brought out to the RCA jack
> and
> the Key-All could be placed in a small plastic project box, external to
> the
> rig, where the MOSFETs can stay floating above ground. If that is done, I
> would definitely move R1 from the Key-All PCB to the inside of the rig as
> a
> current-limiting buffer against accidental shorts.
>
> That's it. If you can tackle this, you'll have the best output key line
> known to mankind: Totally silent and capable of switching moderately
> high-AC/DC-current key line amplifiers.
>
> In other Ten Tec's, I have also replaced the TO-92 style relay driver
> transistor with a 2N5551 (good for +140 VDC), bypassed the relay and then
> brought out the 2N5551's collector to the rear panel RCA jack. That works
> well with most amps, but the Key-All solution is the "real man's" way to
> tackle the problem.
>
> Paul, W9AC
>
>
>
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|