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Project 775

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pjxii:
Josh, I just found this thread. Great stuff and I'm glad you're posting these updates!  I'm learning a lot from them.

I just bought an early 775DSP but won't get it for a couple of weeks. It was finally time to upgrade my Kenwood TS-130V (yes, I said V).

Can I ask what the stock 9 MHz and 455 kHz filters are in this rig?  Mine will have originals but I would also like the wider SSB filters, but with the option to go narrower (like 1.8 khz) when needed. What filters can I fit in the 775 and what would you suggest?  CW using 500 hz would be fine for me and I wouldn't care about AM on this rig, already ordered the Inrad Roofing Mod.  I have my other receivers for AMBC.

I always loved the receiving ability of my (now gone) R-70 but the audio was indeed lacking. The 775 has a very good reputation though.

Josh:
Glad I could help! Also, Wally, my eyes, ears, and steady soldering hands in this project, also is glad you find this interesting. Everyone wave hi to Wally!

On the 455kc and 9mc filtration front, you have several options built in, and some can be retrofitted.

If you are unconcerned about wideband am or nbfm, one thing you can do is change the filter that sits in the output of the 9mc IF amp from 20kc+ to 6kc or so, this alone will do wonders for close in sigs and IF noise getting to the next stage. Just look at my notes where the filters are mentioned and you will get the idea. This filter swap should help approximate the Inrad front end. I got a replacement filter for this position from a HAM radio repair shop and he may have several of each bandwidth, $20 shipped. Pm me for details.

Also, you have to read the manual closely as you have 3 filter settings buttons and one dsp filter setting set via menu, then you have twin pbt and the like on the front panel.

The FL80 9mc IF filter that is present in all 775s is a high quality 2.4kc filter, great for dx and possibly ecssb, poor for audio reproduction of wider signals. It's a pin for pin swap with the older 9mc IF Icom filters such as the FL70, the FL70 matches the FL96 @ 2.8kc wide sitting in the 455kc IF strip. You can find FL70s on ebay, qth, etc, also they are present in any Icom IC-R71 - wich is where I got mine.

The FL96 doesn't need any replacement unless you can find one of the FL257s, I think it is, a 3.3kc wide filter for the 455kc IF and is a drop in replacement but these are scarce and pricey.

If you're a dxer/intend this rig to be a dx machine, you might be interested in swapping the FL96 for a FL44A, wich matches the FL80 in bw and is the dxer sought after xtal filter pairing for the older Icoms, this pairing was standard in the illustrious IC-751A and optional in many other like era Icoms. The good news is these filters can still be found and are in most cases a lot cheaper than back when everyone was looking for them.

I like the filters to match, doesn't make much sense to run a narrow filter before a wider one or vice versa when you desire wider bandwidth audio.

On the narrow mode filters, you can go 300hz or 250hz for the option slot and that might help in cw work and perhaps weak signal modes like ft8 and psk31, keep in mind with the Icom narrow filters, the more narrow you go the worse the shape factor becomes as is usual for very narrow analog filters, but this should be of little concern for HAM work.

thecolonel:
That was an excellent radio for the 1990s time period that it was produced and it cost a pretty penny back then from what I recall. It was in the range of your Yaesu FT-1000D type of transceivers or the equivalent of buying a couple of FT-1000 MP transceivers. I didn't have one at the time as I was as poor as a church mouse but I did have plenty of opportunities to work people that did on my entry level FT 840 etc which was a well known rig for that time as well and relatively inexpensive at about $750 USD around 1997 or so. Then over the next few years I was able to do much better financially and moved up to IC-746 and Kenwood TS-570D and IC-746 PRO etc before I sold a few of them off and bought some other equipment. The IC 746 and the PRO model was a fine radio but the problem was when the LCD screen went out it was about a 400 dollar repair at the time and I didn't think I was technically savvy at the time enough to actually fix it back into perfect working order. I was more of an operator then versus more of a technician now which came with age and experience.

Icom had a lot of nice and semi basic radios going back to that time period such as the IC-738, 728, 729 etc and they weren't horribly expensive its just that I seemed to gravitate to Yaesu gear and such in the mid 1990s plus I had and still have a working FRG-100B that was one of my first REAL radios after I got a real job and bought more than the few portables I had for most of the 1990s. However, I still like playing with portables or just taking my Eton Executive Elite or my Tecsun PL 880 to the park with me when I go to exercise and take a small 20 to 30 foot roll of automotive wire for use as an antenna which is still fun listening at times.

Josh:
A lot of the ft1000 is inside your frog100, they're a very worthy sw set.

:D

I'll do up a Project 775 Care Package with pertinent pdfs and notes and post it at some file host for those interested.

pjxii:
Yes, a PDF report of your work would be a great idea!  The more information readily available always helps.

I got my 775DSP a few days ago (without the manual)  and have been web searching for some answers to a question with no real luck. I understand the DSP HPF/LPF set up for TX/RX, but regarding the analog crystal filters:

Does the 775 use one set filter bandwidth (and IF frequency) to transit in SSB (such as the FL-80) and use the others for receiving only, or does the front panel selector allow using the different filters for transmit?  In other words, would I have a choice of using both an FL-70 AND something narrower (like an Inrad 2.1 kHz) filter for transmiting if desired?  If only one is used for transmit, which filter position is in line during transmit?

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