[TenTec] SB-221 and Omni 6+ question

[Michael O. Hyder]

Hi, Phil and everybody else--

1.  You can print out the schematic in two parts for the SB-220, if you
point to ftp://bama.sbc.edu/downloads/heath/sb220/

2.  From Rich Measures website http://www.vcnet.com/measures particularly at
http://www.vcnet.com/measures/cisb220.html here is what he said about the
transceiver relay:

"Transceiver Relay Contact Failure
    During receive, the voltage across the Antenna Relay Jack rises to about
+115V. A bypass-capacitor, C52, is connected in parallel with this jack, so
the capacitor charges up to 115V during receive. During transmit, the
transceiver's relay (if one is used) places a short-circuit across this jack
and the fully-charged C52. The SB-220 relay coil current is only about
0.025A, but the peak discharge current, produced by placing a direct short
on the charged capacitor, can be surprisingly large. This action is like an
electric spotwelder. In time, the contacts in the transceiver relay can
become pitted and fail to make contact, or become spotwelded together,
causing the amplifier to key-up continuously.
    This problem can be corrected by placing a 100 ohm to 200 ohm , 1/2W
resistor [to limit I] in series with the center pin [blue wire] on the
Antenna Relay Jack. C52 must be connected to the blue-wire end of the
resistor. See Diagram 1.
    The voltage lost in this resistor will = I x R = 200 ohm x approx.
0.025A = 5V, which is insignificant to the 110VDC relay coil."

3.  About tuning:  Do not exceed 200 mA for long, and never exceed 250 mA
grid current.  I run mine on the low voltage position (CW/Tune), but others
just run on the SSB position.  I tune for maximum output power using low
drive, then increase drive to the point that I am getting about the 200 mA
grid current and use the Tune control to peak the output power.  To increase
power, the Load control can be advanced so that when drive is increased, the
grid current does not exceed the maximum.
    I am perfectly content to run 700 watts or so output on 40 meters.  Have
run about 1,300 watts output to see if it could be done, but I just believe
that is pushing it -- it isn't worth the difference to me.

4.  Do not use the ALC jack on the SB-221 with your Omni-6.

Regards, Mike N4NT@chartertn.net

----- Original Message -----
From: <psikes@whidbey.net>
To: <tentec@contesting.com>
Sent: Thursday, December 14, 2000 10:20 PM
Subject: [TenTec] SB-221 and Omni 6+ question
|
| Hello folks, I need some help here. I just picked up a Heathkit SB-
| 221 and woul like to hook it up with my Omni 6+. The problem is
| that there was no manual with the amp. Will the relay on the Omni
| handle the voltage from the amp or do I need to build an interface?
| Not having the manual is a real pain, if anyone has one of these
| amps could you pass along the tuning procedure you use please.
| My main amp is the QRO HF2500DX and the tuning method for it
| is quite a bit different from a standard amp.
|
| Thanks and 73 - Phil
| N7UX



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