[NLRS] 2304?
Dr. Gerald N. Johnson
geraldj at netins.net
Thu Dec 29 22:58:58 EST 2016
On 12/28/2016 9:45 PM, John Toscano wrote:
> Jerry:
>
> The 4-connector transfer relay that I got from W0GHZ for my 10 GHz rig
> switches the antenna feed between the preamp input and the PA output (of
> course), and whichever of those two devices is NOT selected is switched
> to a 50 ohm SMA load. If you used two of them to take a common RF
> transverter connector to split it to a preamp and PA and thence combine
> signal paths to the antenna feed, the PA input and output should not be
> shorted to one another, they should both be connected to a 50 ohm load.
> (2 transfer relays plus 2 independent 50 ohm loads.)
That is very true. I was using such a transfer relay on my 10 GHz rover
for several years as the T/R relay with the termination on the 4th
connector. It developed loss, probably from poor sequencing and I have
gone to a more conventional SPDT coaxial relay.
Either you are wrong
> (something that does not happen often in my experience) or W5LUA is
> talking about some funky transfer relays that don't resemble mine.
Besides the connection above there are two more ways to use the transfer
relay. Look at the relay from the connector face with the connectors at
the top left, top right, lower left, and lower right corners. In one
position the top two connectors are connected inside along with the
lower two connectors. In the other position, the two left connects are
connected along with the right two connectors. In the first position the
top connectors are not connected to the bottom and in the second
position the left connectors are not connected to the right connectors.
When used to insert something, like an amplifier or a filter or
attenuator or any other device of interest with a single relay, the
amplifier is connected between the top left and top right (or any other
adjacent pair of connectors) and the source is connected to the bottom
left and the load (such as the antenna) to the bottom right (or the
ports not connected to the amplifier). Unfortunately when the amplifier
is removed from the transmission circuit it is shorted. So its important
to remove power. This is easily solved by using two relays, transfer
switch or SPDT IF the device being switched can survive with an open
circuit load. Its fairly important to take power off the amplifer during
the time period of the transfer relay changing positions, probably 20
ms, I'm sure the bigger the relay the slower it is though in a couple
printed Transco catalogs I just checked all the transfer switches are
rated at 20 ms max with 28 volts applied. Even when using the connection
above there is going to be a time period when the switched device isn't
terminated.
I looked up W5LUA's article, was in MUD 1999. There he hooked an
amplifier diagonally to the transfer switch, then hooked source and
antenna to the other two connectors. That way with the relay on one
position the amplifier can act as a preamp and in the other position as
a low power transmit amplifier. His application was at 24 GHz and he
noted that the preamp could stand the -10 dBm or so output of his mixer
and produce a useful signal level for transmitting. He also noted it was
important tu use a sequencer to take power off the preamp while the
transfer switch was changing positions so it didn't oscillate and damage
itself with its input and output not terminated. So a third way of using
the transfer switch.
73, Jerry, K0CQ
>
> 73 and season's greetings from balmy South Texas, EL09vu20 de W0JT/5
>
> On Wed, Dec 28, 2016 at 9:27 PM, Dr. Gerald N. Johnson
> <geraldj at netins.net <mailto:geraldj at netins.net>> wrote:
>
>
>
>
>
> On 12/28/2016 8:48 PM, Larry Peterson wrote:
>
>
>
> Excellent to see some interest in 2304 Mhz. Karl WD9BGA and I each
> bought transverters from SG-Labs. See
> http://www.sg-lab.com/TR2300/tr2300.html
> <http://www.sg-lab.com/TR2300/tr2300.html> We also have 33cm
> and 23cm
> units. I use this in sport radio during the warm weather when I
> activte
> SOTA summits or work hams via pre-scheduled contacts from
> lookout towers
> in WI. I operate 2m, 125cm, 70cm, 33cm, 23cm and 13cm SSB and
> CW, but
> given the 50 pounds of equipment I carry up 12 to 35 stories, I
> choose
> perhaps three bands I'll operate in a given morning.
>
> I was very surprised how well the 13cm unit works. Karl & I
> each used a
> small circuit board antenna that comes with this Bulgarian
> transverter.
> We were 8 miles apart and we had S9 or better SSB signals. I then
> rotated my tiny antenna broadside, and Karl's sig was still very
> strong.
>
> Karl & I set the North American summit-to-summit record this summer
> using a 79 milliwatt MESH system and Pidgin chat mode on 2.4
> GHz. That
> was completely LOS. We tried twice more and could not repeat the
> contact, so we are realizing how special that ultra-low power
> microwave
> contact was.
>
> Now in real operation, I will use my 27-element Directive
> Systems loop
> Yagi, with the SG-Labs transverter, with 70cm IF. Per my Bird
> wattmeter
> it puts out 2 Watts.
>
> As far as an amp, I could use your help, Jerry. I like the PE1RKI
> design. He has many options. See
> http://www.pe1rki.com/40watt13cm.html
> <http://www.pe1rki.com/40watt13cm.html> I have sufficient
> LiFePO4 battery
> capacity to run one. I wouldn't mind putting out 25 or so
> Watts. But
> my problem is I do not know how to set up the T/R relay switching.
> Anyone with ideas would be appreciated.
>
>
> That's where you need a sequencer. If your transverter has two coax
> connectors, on for receive and one for transmit, then you can add
> the PA to the transit side and go to the TR relay. RF relays don't
> survive well with RF present while closing or opening, and PA's
> don't survive well with full RF drive and the relay open for 10
> milliseconds or so. Unfortunately virtually all IF rigs put out RF
> before they put out the TX output control line. One way to sequence
> is to run the microphone PTT (VOX not allowed, nor KOX) through
> auxiliary contacts on the TR relay but key the relay with the
> microphone PTT first. Paul Wade has a couple sequencer designs on
> his web pages, and there have been several published over the
> decades. On 10 GHz I thought I had some sequencing using the TXinh
> line of the IF rig with some delay on a transistor switching that
> bias off a modification of the DEMI TC, but my 10 GHz TR relay
> suffered. Now I have the IF (FT-857D) set up for PTT only for SSB
> and CW tx only with the PTT on the microphone pushed. So I'm using
> manual sequencing, manual PTT, then give it audio or start keying.
> Stop the audio or keying before releasing the PTT. Its working
> depending on the SSB transmitter not transmitting a crunch from the
> PTT switch or some kind of transmitter transient which isn't impossible.
> http://www.geraldj.networkiowa.com/papers/CSVHF2010/TxinhtoTC.pdf
> <http://www.geraldj.networkiowa.com/papers/CSVHF2010/TxinhtoTC.pdf>
>
> DEMI will sell their TC board kit separately from transverters. I
> have bought a couple for future projects.
>
> If the transverter has only one RF connector, you need two TR relays
> to switch the PA in and out or one four connector transfer relay.
> I've been looking at lots of proceedings lately and W5LUA did have
> an article on applying the transfer relay in one of them. Possibly
> on the technical section of the NTMS web site. The only problem with
> a transfer relay is that it connects the PA input and output
> together when not using the PA so the PA has to be disabled to keep
> it from oscillating destructively.
>
> 73, Jerry, K0CQ
>
>
> 73,
>
> Larry WA9TT
>
>
>
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