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Author Topic: Manual for the WJ-8716/18 Available  (Read 25038 times)
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WA1GFZ
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« Reply #25 on: April 16, 2007, 02:39:36 PM »

Tom all you need to do with the 8716 to bring it to an IP3 of plus 30 is increase the LO to the first mixer and replace it with one that will handle 1/2 watt of LO and put a better post amp after it and you are there.
The next step is an H mode or FET ring with better roofer.
Networks internation built many of the roofers and all performed about the same. The power limit of a crystal is plus 10 dBM. The  next step is to run a pair off quad hybrids.
This was a very well designed RX that will be around for a long time.
It was one of the best for 1970s design.
The AM detector is pretty simple so operating level must be good.
 
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Tom WA3KLR
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« Reply #26 on: April 16, 2007, 03:38:05 PM »

Frank, all you need to do with the 8716 to bring it to an IP3 of plus 30 is put a 10 dB. pad on the input.  A hell of a lot easier and quicker.

If I had one here and put a 10 dB. pad on it, it wouldn't make a bit of difference anyway.  No BC or SW sites near here.
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73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
WA1GFZ
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« Reply #27 on: April 16, 2007, 04:08:49 PM »

That's fine if you can handle the MDS 10 dB higher.
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Steve - WB3HUZ
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« Reply #28 on: April 16, 2007, 04:29:37 PM »

Unless that receiver is deaf, then a 10 dB pad will mean no difference in reception capability on the lower bands (unless you have an exceptionally quiet location). Average noise at those freqs allows for something like a 20dB noise figure without affecting MDS.
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WA1GFZ
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« Reply #29 on: April 17, 2007, 08:44:56 AM »

No problem on the low bands I run a 1:4 splitter most of the time but up on 15 and 10 it will hurt you. The RX doesn't have an RF stage so can't handle any more attenuation.
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Tom WA3KLR
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« Reply #30 on: April 17, 2007, 11:49:45 AM »

I've been studying the W-J section in Fred Osterman's Shortwave Receivers book.  I see that the WJ8711 followed the 8718.  Any comments on the 8711 and 11A?
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73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
WA1GFZ
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« Reply #31 on: April 17, 2007, 12:26:02 PM »

8711 and the later 8711A are DSP rigs. the 8712 is the same stuff in a 1/2 rack. the 8712P has a front panel with controls.
I don't know the front end but uses a DSP for demodulation. I seem to remember last IF was 16 KHz into the DSP.
They sell for big money. I've seen them over $4K.
I've never operated one but saw an 8711 once.
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w3jn
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« Reply #32 on: April 17, 2007, 01:05:43 PM »

8711 is OK, lotsa bandwidths to play with but I prefer the 8716/8718 for simplicity.  At least the 8711 has a real front panel and tuning knob, vs the Collins 95S which relies upon a mouse and crummy proprietary computer program for control.  The 95S is a pretty decent performer though.
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Tom WA3KLR
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« Reply #33 on: April 19, 2007, 04:46:02 PM »

Frank and all,

In the early 1980’s I used to do A LOT of short wave listening with my R-7.  In that time period, a local ham was selling a switchable 25 dB attenuator at a hamfest so I bought it.  I kept it on my R-7 input and would switch it in when I listened to strong SW stations, not that I needed to, but because I could, I guess.  I did this mainly with Radio Moscow, the strongest signal I ever heard.  They came in at 60 dB over S-9, yes 10 dB stronger than Ken W2DTC. 

When I switched in the pad I would think wow, my 3rd order input intercept is now +50 dBm., not a station in the world can touch Radio Moscow. 

Then I would sit back and listen to the butt-sucking BS of Vladimir Posner and the grind of the 50 Hertz 3-phase ripple.  STRAPsky.
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73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
WA1GFZ
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« Reply #34 on: April 19, 2007, 09:23:36 PM »

Back in the 70s I built a hot rod SB303 with three filters cascaded in the IF and a tracking first IF with double balanced mixers. I used to park myself as close to commie radio as I could and operate on 40 meters. back then I took the dynamic range from 67 db to the mid 80s. I dreamed of 90 dB dynamic range.  I then bought a TR7A that ran about 95 dB but the filter blowby limited the performance.....and I dreamed of 100 dB of dynamic range.  Now I have 100 dB and dream or more....
or I could sit on the beach and dream of wild life.
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WA1GFZ
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« Reply #35 on: April 20, 2007, 11:19:29 AM »

Just looked up the post mixer amplifier and it would support a mixer ahead of it rated for plus 30 dBM IP3. So all you need to do is jack the LO up and change to a better mixer and you have a RX as good as most of the best made today. not bad for a 30 year old radio.
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