There is nothing magical about a front end saver, IMHO. Several years ago I
built my first, a simple unit employing a pair of Panasonic PCB-type relays
which grounded both the RX antenna port on my transceiver and the beverage
antenna input to the preamp/switching system on transmit. As long
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,
Bill,
I don't know the complete list of radios that need one, but I do know that
more than one IC-751A and IC-765 have been damaged without some kind of
protection against RF getting in through the separate RX ANT input.
73, Mike
www.w0btu.com
On Sun, Aug 30, 2015 at 6:08 AM, Bill Liz
How about back-to-back 1N4148 diodes (2 in series) across the RX path, and
a #47 incandescent lamp between those and the Beverage? That's what I do
here, among other things.
Those are in series with my preamp, which is almost always on. There's also
some variable resistance in series with the
I have also used bi-directional 1N4148 diodes across the antenna path, but
I'm re-thinking that approach - If the diodes are not preceded by a good
bandpass - or at least, a hipass filter in the antenna lead, I'd be
concerned in some instances about the possibility of intermod from nearby,
or
The mast of my RX flag is 20-25 ft from my 160/80m shunt fed tower. I run a KW+
on the low bands. I use an Array Solutions AS-RXFEP RF Limiter (aka FES etc.)
in line with the flag at the rig’s RX Ant IN. The RXFEP uses a gas discharge
tube and a pair of matching transformers with back-to-back
Array Solutions offers a 'RX Front End Protector' based on back-to-back
1N4148 diodes.
Schematic:
http://www.ok1rr.com/public/rxfep.png
more details:
http://www.arraysolutions.com/Products/as_rxfep.htm
manual (also pictures of clipping etc.)
There is nothing magical about a front end saver, IMHO. Several years ago
I built my first, a simple unit employing a pair of Panasonic PCB-type
relays which grounded both the RX antenna port on my transceiver and the
beverage antenna input to the preamp/switching system on transmit. As
long
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
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
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
Tom -
Maybe we should say backwards T/R relay when we mean the reverse, of
what we did with real T/R relays when I was a kid. All of my rigs used
120VAC outboard relay coils!
FT-747 is indeed notorious for T/R timing issues, its semi-break-in so
severely truncating the leading element on CW
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
Tom is right about this thread splintered. It is bugging me to hear several
very common misconceptions going on for years.
1- A preamp is part of the radio, not the antenna. As such, when you add a
preamp, you are changing the RADIO performance, not fixing the antenna gain.
For low bands IP3 is a
On Sun,8/30/2015 7:32 AM, Larry wrote:
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.
My neighbor, Bob Wolbert,
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.
Done properly, it doesn't hurt a thing. The proper way is to use
That's similar to mine, but mine has two 1N4148 diodes in series,
back-to-back, total of four diodes.
However, after I did that, I got to thinking that it would be better with
only two. Or that there was no need for four. (Don't ask me to explain,
it's been a long time since I've thought about
I read it a long time ago on Measures; website. I never used it. I didn’t have
an SB220. I just remembered that it was a relay speed up scheme. I mentioned it
just in case may help with speeding up a slower relay. The original poster
would have to consider if the scheme would be suitable under
That's similar to mine, but mine has two 1N4148 diodes in series,
back-to-back, total of four diodes.
However, after I did that, I got to thinking that it would be better with
only two. Or that there was no need for four. (Don't ask me to explain,
it's been a long time since I've thought about
Martin, Tom and all members of the list,
The AS RXFEP is very nice but it is very expensive.
I prefer the KD9SV modify by Martin, OK1RR...it is very easy to build but i
need only the relays...someone can help me to get those relays ???...are
they available at digikey or mouser ???
The
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.
Hello to All;
Many years ago Alpha used a very nice QSK sequencing circuit for the Alpha 77,
NOT 77DX,D,SX, just the plain 77 ( 1971). It used a RJ1a and a reed-relay, a
couple of diodes and a resistor. It was powered with 55 volts. Worked very good
and I have the diagram. I have used it for
Mike,
The Array Solutions device also uses the transformers to increase the
voltage at the diodes then steps it back down which means that the diodes
are not doing their limiting at 50 ohms. Therefore, your set of 2 series
diodes or even one diode each direction is limiting at a higher power
Perhaps common-mode isolation of currents induced in the antenna coax shield??
Charlie, K4OTV
Lee K7TJR k7...@msn.com wrote:
Hmmm, I wonder why the Array Solutions circuit board picture shows MCL 1:1
transformers.
Sounds fishy to me. Even the waveform pictures show clipping at a
Well, that's certainly true, Lee. I was just wondering aloud, if the
transformers were indeed 1:1, if the point might be common-mode isolation
like we work to achieve in the transformers of our flag, pennant and KAZ
antennas - although in those cases the matching transformer also matches the
Since I am the original reason that Gary KD9SV built the first Front End
Saver device after we determined why I blew the front end many many
years ago of my IC-765 radio. I thought I might add one more very important
thing to what ever version of a Front End saver you guys decide to buy or
Sorry Charlie, I don't think I made my thoughts very clear.
James was quoting from a QST article that there was an impedance
transformation because of the transformers.
This was to make a higher voltage at the diodes. My point was that if the
transformers being used on their circuit board
I believe the point of having the transformers in their circuit is to
limit the maximum output.
A transformer (ferrite in this case) can only output whatever maximum
current determined by the core saturation level. They are relying on this
property of the transformers to limit the current into
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