Search found 73 matches

Return to advanced search

Re: Juma TRX2A Low Mic Gain. Problem solved.

Robert,

Good to hear that :D

Readjust now the SSB gain trimmer R26 for 10W peak RF ouput. Typical proper value is in the middle position approx 25kohm which can be measured with ohm meter when TRX2 is OFF.

Enjoy QSOs with your JUMA TRX2.

Happy New Year
73 Matti OH7SV
by OH7SV
03 Jan 2012 18:29
 
Forum: Juma Discussion
Topic: Juma TRX2A Low Mic Gain
Replies: 3
Views: 3881

Re: TRX2 Microphonics

John, During the design phase I tested several cap types for C4...C7 and C12...C15. Murata GRM31M5C1H473JA01D (grey in color) caps performed very well. I wonder if the brown caps you got with the kit are Murata type. Your modification idea is good. I have also sketched quite similar circuits. You ar...
by OH7SV
03 Jan 2012 16:32
 
Forum: Juma Discussion
Topic: TRX2 Microphonics
Replies: 5
Views: 4117

Re: Juma TRX2A - Voltage supply problem in Main Board

Saku, By default ICs are not broken if you have not overstressed them with wrong polarity or some other "brutal" way. Additionally LP2951 is not very sensitive for ESD. There has not been any problems in TRX2 voltage regulators. You must have something wrong. Check carefully visually every...
by OH7SV
03 Jan 2012 08:58
 
Forum: Juma Discussion
Topic: Juma TRX2A - Voltage supply problem in Main Board
Replies: 17
Views: 14245

Re: TRX2 Microphonics

John, The AF gain is huge but typically there has not been problems with acoustic feedback. I guess you have tested with an external speaker. Is it ok? Please check that the main board capacitors C4...C7 and C12...C15 are right G0G type. The G0G color is grey compared to the X7R brown color. X7R typ...
by OH7SV
03 Jan 2012 08:26
 
Forum: Juma Discussion
Topic: TRX2 Microphonics
Replies: 5
Views: 4117

Re: Juma TRX2A Low Mic Gain

I have 0.9 volts on the electric mic hot side Robert, Something is wrong with the electret mic biasing or in the mic or in the wiring. The mic "hot side" voltage should be much more than 0.9V. Typical electret mic current is 200uA...300uA. That means 3V...4V on mic hot side. Please check ...
by OH7SV
03 Jan 2012 08:10
 
Forum: Juma Discussion
Topic: Juma TRX2A Low Mic Gain
Replies: 3
Views: 3881

Re: JUMA PA1000 Linear Amplifier

Hello Kevin and Ron, Nice to hear that you are interested in Juma PA1000. I appreciate all your comments. Ron, I understand your comment on the separate RF section. The reason to the design is that I am seeking simplicity and reproducibility because I like it and I don't like the popular hassle cons...
by OH7SV
23 Dec 2011 22:47
 
Forum: Juma Discussion
Topic: JUMA PA1000 Linear Amplifier
Replies: 50
Views: 97834

Re: Where are TRX2 Noise Blanker and Voice Memory located?

Daniel, 1. Noise Blanker option has not been launched. The intented location in the main board is (was) the pin header between Polyphase and 1st filter. We made few Noise Blanker prototypes but we did not get good enough results. The technical reason is that the bandwidth is too narrow to detect fas...
by OH7SV
21 Dec 2011 10:53
 
Forum: Juma Discussion
Topic: Where are TRX2 Noise Blanker and Voice Memory located?
Replies: 1
Views: 2292

Re: Teflon wire

Frank, Thank you for a good advice. I purchased shielded Teflon wire from the johnswireshop.com Here is one link http://stores.ebay.com/Johns-Silver-Teflon-Wire-Shop/Shielded-Wire-Coax-/_i.html?_fsub=3966787&_sid=155009&_trksid=p4634.c0.m322 The wires look good and he price is preferable. I ...
by OH7SV
13 Dec 2011 21:23
 
Forum: Juma Discussion
Topic: JUMA PA1000 Linear Amplifier
Replies: 50
Views: 97834

Re: JUMA PA1000 Linear Amplifier

Do not waste your money on 25 ohm coax. #24 single shielded Teflon wire is very close to 26 ohms. Frank, tnx for the good advice. What do you say about this Teflon cable? http://www.ebay.com/itm/25-24-AWG-Shielded-Silver-Teflon-Wire-Coax-/230603278042 BTW, have you measured other gauges of shielded...
by OH7SV
29 Nov 2011 19:52
 
Forum: Juma Discussion
Topic: JUMA PA1000 Linear Amplifier
Replies: 50
Views: 97834

Re: JUMA PA1000 Linear Amplifier

Hello Bob, Thanks for very informative reply. Nice to hear that you are also experimenting the Freescale MOSFET. Actually I don't know anybody else who is doing something in HF with the MOSFET. Sorry to hear about your weak results. I think that the harmonics are related to incorrectly operating RF ...
by OH7SV
17 Nov 2011 18:06
 
Forum: Juma Discussion
Topic: JUMA PA1000 Linear Amplifier
Replies: 50
Views: 97834
PreviousNext

Return to advanced search

cron