Having installed a synchronous detector board into my R71a, there was the need to select between it and the original AM detector, without defacing the radio by adding extra switches to the front or rear panel. After studying the circuitry around the mode select IC13 on the logic unit board, there is an unused pin 1 that can be used for this task. Remove Diodes D10 and D13 from pins 32 and 36 on IC14. Add a long wire to pin 1 of IC13, best done at the unused pin at J2. This wire will now go high when FUNCT/CW is pressed, .... the same way as FM is selected by pressing FUNCT/AM. For my situation, I routed this wire through to the main board, through a switching diode, cathode to AM pin on J12. This enables AM mode when high. The added`wire also connects to the base of Q25 through a series 4k7 resistor, and a switching diode, cathode to base. This disables the normal AM detector when high. The voltage on this wire also is used to enable the Synchronous detector board. In use, all mode functions are as normal, pressing FUNCT/AM will select FM, AM will select normal AM, now pressing FUNCT/CW will select the new Synch AM, The ICOM memory will also store the new synch mode together with frequency. Unfortunately, there is no spare or unused icon in the flourescent display to activate with the new mode, so when selected, no mode icon is visible. This switching arrangement has many other uses and saves having to mess up the appearance of the radio. When working on your radio, take your time, and understand what you are doing. Disconnect power first.

Can you tell us what kind of synchronous detector board you have installed ?
Do you have any pics ?
Regards.

The detector is a homemade design using a phase detector to lock the Icom 2nd local oscillator to the carrier. I dont know how to post pics. Cheers.

This fine RF-590H is up for bid to the highest bidder for the next 5 days.
Let me know what you think its worth. I'm thinking the bidding should begin
around $1500. Let me know what you will bid. Bid at ... I
will end it at 9:00 pm PST on Feb 12, 2010 and notify the sucessful bidder.
I will leave a public note as to the outcome of this auction.

http://s1022.photobucket.com/albums/af347/n6jp/ (Be sure and click on each
picture to enlarge it for a better look.)

It is my pleasure to be able to bring this Harris RF-590H premium receiver
to the community as it is one that rarely comes up for sale anywhere. These
receivers were built to exacting military standards using the highest
quality components and modular engineering. Stability of this receiver is
listed at + or - 1 part in 10-6 with a 5 Mhz TCXO standard. What does that
mean? The circuitry in this receiver is rock solid!
The RF-590H was originally used in the US military (mostly Navy) and
diplomatic institutions (Embassies) for communications and surveillance from
1982 to about 1998 when it was replaced by the RF-590A.

This "H" version of the RF-590 is coined the "hopping" or "agility" version
due to it's special scanning of channels and the ability to zero in on
frequencies from other cooperating parties much more quickly. According the
the Harris patent for this model, it could take about 10 to 15 minutes to
scan and locate a transmission since transmissions may be intermittent and
on unknown frequecies. Harris designed special circuitry to allow the
operator to locate these transmissions much more quickly. I do have a
special manual for this "H" version. However, for practical listening, the
included full manual should allow for most common operations. If you care
to see portions of the manual prior to bidding, you may look he

http://www.premium-rx.org/rf590.htm

This RF-590H is built for 19" rack mounting and is a heavy, rugged radio
measuring a depth of 20.5 ", height of 5.25" and weight of around 40 lbs (50
lbs shipping). Inside, each stage is enclosed within a separate shielded
box to minimize birdies. A large aluminum knob and numeric keypad permit
tuning FM, AM, SSB, and CW signals in the 0 to 30 mhz spectrum. The
frequency resolution is down to the individual Hz and is broken out to the
full 3 decimal places on the bright blue vacuum flourescent display.

The RF-590H has the option of 4 AGC settings, and filters of 6.8 khz for AM,
3.2 and 2.7 Khz for SSB both upper and lower, and 300 Hz for CW. I have
taken a picture of these crystal filters inside the top of the unit and it
appears like there is one slot open for another filter, if desired. Just a
quick note, if you think that the AM filter of 6.8 khz it too wide, based on
past experience with other receivers, you would likely be correct. However,
the tuning on this Harris is so precise, you can tune into an AM signal and
if a narrower bandwidth is required, switch into SSB and chose upper or
lower with amazing results. I have found that there are few good receivers
that will allow this without serious degradation of the sound quality, but
you hardly notice with this Harris. This tactic alone has allowed me to
copy AM signals on shortwave that my other highly tricked out receivers
using passband or a sync detector struggle with.

The RF-590H has 100 memory channels and memory scanning of these channels.
I mention this as I rarely ever use memory channels, but others find this to
be a large benefit when listening.

One thing that will tell you that this is a high end receiver is the modular
design. The receiver is a BITE built in test button. Once depressed, the
receiver runs through a series of audio, display and circuitry tests
(processor EPROM, Processor RAM, synthesizer lock, rf signal path, and IF
signal path) and will either display "passed" or give a fault # on the
display and light the red fault light on the front panel. The owner's
manual gives the fault codes so you know where to look for the problem
(called fault isolation). As you can see in my picture, this receiver
passes with flying colors, but if it would not, replacing it with an
available module/board would be a snap. Now if only the auto industry would
do this with our automobiles instead of us trotting off to drop money for a
dealer to run such a test.

Speaking of owner manuals, it comes complete with a full set of manuals that
cover the RF-590H receiver. These manuals have both operating instructions
and schematics covering this fine receiver.

This Harris RF-590H is microprocessor controlled receiver and due to the
exacting standards in build, originally sold for $17,900 to the military.
This receiver is categorized as a premium receiver and there is a group of
premium receiver owners online that assist each other with questions such as
operation, location of parts, repairs, mods, etc. You can find that site
he

http://www.premium-rx.org/

Other features of this Harris include a 1/4" headphone jack in the front, an
RF gain, a BFO that operates + or - 9.9 khz in 10 Hz increments, and a whole
series of terminals on the back that provide pre and post IF filtered 455
khz jacks and a whole host of interfaces for use with other equipment or
with remote devices.

I have mentioned all the the main features of this RF-590H except for one.
And from my perspective, it is one of the strongest....the audio circuitry.
Unlike amateur radios or consumer shortwave radios, professional
communications receivers have been designed for hours of monitoring with a
minimum of knob twisting. This Harris receiver works some magic with the
audio circuits, bandpass filters, and automatic gain control. Besides news
broadcasts from foreign broadcasters, I have enjoyed listening to music on
the shortwave bands by piping the audio into a "Sounds Sweet" speaker that
sits on my desk. The low frequency content is surprising as this is often
removed from receivers to "improve" intelligibility, but Harris leaves it
in. Typically, taking the audio into a larger speaker would result in a
painful experience, but with this Harris receiver, the result is so
pleasant. As is the custom with all communications receivers, the onboard
speaker does not do justice with this receiver's audio capabilities.

I doubt that there are many better receivers built for broadcast AM audio.
If I am doing work where I don't have to concentrate, it is a nice departure
to tune into the 80, 40 or 20 meter bands to listen in on some of the
amateur radio nets. The SSB on this receiver sounds unlike anything on my
other communications receivers!

Electrically, this Harris works just beautifully. I have tested it over the
past few days and it has been a joy. Cosmetically, this receiver is in very
good condition. There are the usual nicks and smalI scratches that one
would expect to find on a older piece of gear. However, the circuitry and
internals are perfect so this is cosmetic only.

At this point, I hope I have covered anything that may be a question for
you. However, if I have overlooked something, please email. Most questions
will be with regards to shipping.

However, there will be a charge of $150 for double boxing and shipping this
fine receiver anywhere in the lower 48 states of the U.S. This allows me to
pack well so that it will arrive undamaged. Anywhere else will cost only
enough extra to pay to the destination.

I can ship this unit overseas, but it is not my desire to do so due to the
high cost of shipping. The cost will likely run $400, $500 or even more and
I won't know until it is fully packed at the end of the sale. If you have
the means to pay these high shipping charges, I don't mind working with you.
However, due to the nature of the cost being tied into both the weight and
the size shipping box, I am unable to give a quote for shipping until the
receiver is fully packed after the auction ends. Thank you for
understanding!

The winning bidder is asked to pay within 5 days. You may pay via cash (if
picked up), or US Postal money order. I will not ship until full payment is
received and processed.

This excellent reciver is offered as is with no guarantees implied or
offered. No returns or refunds are offered to the buyer of this unit.

Contact me at with your questions or bids. I live in the
93312 zip code area of the U.S.A.

regards, Jerry