Anyone got the info on this? And particularly the transistor(s) involved ? THX - '73 - Rumrunner out.....
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Shottkey diode conversion for RCI-2980?
- Thread starter rumrunner
- Start date
The PCB should be an EPT-6900 10Z
Replace Diodes D30 and D31 (AM detector diodes) with ECG583 Schottky diodes.
Replace Diodes D1 and D2 (NB diodes) also with ECG583 Schottky diodes.
Also replace Q17 (or marked TR17) which is the RF amplifier with a 2sc2999 or NTE107. These transistors provide slightly more amplification and have a lower noise factor than the stock 2sc1674 transistor.
BTW... I have not seen any increase in bleedover after doing these mods. On the Galaxy DX-949 that I did, I saw a 1/2 S-unit decrease in noise floor and a 1/2 S-unit increase in received signals. When doing a comparison between the 949 and a stock DX-2547 (same board) there was a noticable improvement in the 949 over the 2547 not only in noise floor and signal, but more importantly in the signal to noise ratio. The same signal was a clearer and slightly stronger copy on the 949 as compared to the stock 2547.
In my opinion....it is definitely worth performing the mod.
Replace Diodes D30 and D31 (AM detector diodes) with ECG583 Schottky diodes.
Replace Diodes D1 and D2 (NB diodes) also with ECG583 Schottky diodes.
Also replace Q17 (or marked TR17) which is the RF amplifier with a 2sc2999 or NTE107. These transistors provide slightly more amplification and have a lower noise factor than the stock 2sc1674 transistor.
BTW... I have not seen any increase in bleedover after doing these mods. On the Galaxy DX-949 that I did, I saw a 1/2 S-unit decrease in noise floor and a 1/2 S-unit increase in received signals. When doing a comparison between the 949 and a stock DX-2547 (same board) there was a noticable improvement in the 949 over the 2547 not only in noise floor and signal, but more importantly in the signal to noise ratio. The same signal was a clearer and slightly stronger copy on the 949 as compared to the stock 2547.
In my opinion....it is definitely worth performing the mod.
Great! Many thankx. The shottkey's I have are 1n5711's. Will they work or do I need to order the ECG's? Thankx, Ronin! Rumrunner out......
Toll_Free
Well-Known Member
The ABSOLUTE best diodes to use for receiver and NB conversions are the BAT85 diodes. RF Parts and Mouser, as well as most others have these.
I've spent about 90 dollars in different diodes... These work the best. BEST switching turn on that I've found, and the LOWEST turn on thus far.
I'm working on a FET conversion for the first RF amp... Something Bill Good and Justin did, but seemingly was lost in the conversion to the new web board...... SO, time to re engineer the thing
Incidentally, you can get a couple dBs of compression usually by wiring in a couple BAT85s in your mic jack. The turn on voltage is low enough that POWER mic level signals will cause the diodes to conduct. You can wire them as a clipper (anode to cathode, basically shorting them out, then one end to hot, one end to ground), or cut the wire that feeds the audio circuit and wire them in there in SERIES... You'll also want a RC filter afterwards to clean up any harmonics the diodes create.
Merry merry!
--Toll_Free
I've spent about 90 dollars in different diodes... These work the best. BEST switching turn on that I've found, and the LOWEST turn on thus far.
I'm working on a FET conversion for the first RF amp... Something Bill Good and Justin did, but seemingly was lost in the conversion to the new web board...... SO, time to re engineer the thing
Incidentally, you can get a couple dBs of compression usually by wiring in a couple BAT85s in your mic jack. The turn on voltage is low enough that POWER mic level signals will cause the diodes to conduct. You can wire them as a clipper (anode to cathode, basically shorting them out, then one end to hot, one end to ground), or cut the wire that feeds the audio circuit and wire them in there in SERIES... You'll also want a RC filter afterwards to clean up any harmonics the diodes create.
Merry merry!
--Toll_Free