> I know Tom W8JI has worked closely with Ameritron in the past. I
> wonder if he might know how that relay was spec'ed or if there is any
> history on it he could share with us.
Hi Dick,
I didn't have a chance to answer the original question, but let me
give a general reply about relays...since it will apply to ANY
amplifier and ANY antenna switch and be useful to anyone dealing
with signal switching relays of ANY type. This includes 4-squares,
remote antenna switching systems, and indoor devices like
amplifiers.
The relay is the amplifier is the same family of relays used for the
last 30 years by almost everyone, Drake, Collins, Heathkit,
Dentron, etc. You find that relay or family of relays in RCS-8's and
many other antenna switches.
The most common complaint is failure to receive signals without
attenuation, or intermittent receive. In order of most commonly
seen problems:
1.) The contacts have tiny specks of solder flux spattered on the
contacts when people solder around them. You should ALWAYS
cover the contacts when soldering in the area of the relay. In this
case you should use a glossy PAPER soaked in a pure light
hydrocarbon like methyl ethyl ketone, a paint reducer, xzyelne, or
even pure alcohol (not stuff mixed with water) and draw it through
the contacts several times with the contacts held against the
paper.
2.) The relays get specks of dust or other insulating trash between
the contacts. In this case you should simply degrease the
contacts with a fast evaporating pure clean solvent and blow them
out with high pressure air.
3.) Smoke deposits or a film of contaminants (common in the
disgusting smelly equipment used by smokers, or in industrial
areas). In this case they need cleaned like above.
The most common thing everyone "screws up" is they remove the
gold flashing off the contacts by cleaning the relay with an
abrasive, like a contact file. If you use an abrasive, you have
trashed the relay. The gold flash is necessary because there is NO
contact current on receive. Without contact current, the relay can't
"burn" through any garbage. (Burning through the garbage is why
sometimes when your receive is out and you "bump" power through
the contacts it restores the receive.)
Another big problem is the contacts, in order to handle 10-15
amperes on transmit, are designed wrong for handling almost zero
current on receive. That's an engineering conflict relay designers
are VERY familiar with.
By the way, Ameritron is gradually switching to a compact
hermetically sealed high-current miniature relay. That relay is in the
current production runs of bigger amplifiers (on a circuit board with
sequencing control components and a speed up circuit), and
shortly will be in revised RCS-4 and RCS-8 (now eight positions
and BCD three-wire controlled) antenna switches. It will be in the
rest of the amplifiers as new circuit boards are ordered.
I'm also just finishing a "smart switch" that actually can learn what
antenna you use on what band, and go to that antenna
automatically. It includes amplifier lock-out while switching so you
can "hot-switch" if you want to change antennas while transmitting.
The control unit is compatible with other systems, like 4-square
systems, so you can change directions while transmitting without
blowing up relays.
73, Tom W8JI
W8JI@contesting.com
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