Nouveau 75 Microphone to D104 Modification - Amplifier Keyer and Speaker output.
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- Опубликовано: 23 май 2022
- This little 75 meter AM transceiver has beautiful transmit audio if you just replace the mic. with a D-104 crystal mic. No preamp is needed.
I also included a simple mod to key your amplifier plus how to bypass the headphone resistor for enough audio to drive a big speaker.
Here's the link to the new mic. cable.
www.amazon.com/dp/B0813C1FFD?...
Almost any silicon NPN transistor can be used to key a modern amp. Look up the maximum emitter / collector current and compare to your amp's needs. If you use an older amp that needs high voltage and current to key it then use an amp keyer such as this in between:
www.hamgadgets.com/UKA-2
or
www.dxengineering.com/parts/a...
I don't use anything. I can easily key the RF-Kit amp or any Elecraft plus tons of other modern amps.
Using an amp with LDMOS PA you can easily get full legal output since these require very amounts of drive power.
I get 6 watts out of the Nouveau 75 after removing one turn from L4. 100% AM modulation and 110% positive peaks at 1200+ watts PEP. 
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I just ordered mine. I did homebrew mics made from non-working Xtal headsets. I slice them open, and add modern electret mics and re-seal them. Some are used with the EL-84 AM TX that I built. I ordered mic cable that U showed and will try getting it together.
Just keep in mind that that mic cable isn't shielded. I didn't notice that until later. Now I would look for something else but there's not a lot to choose from.
Nice.................
Hello Steve, Nice video. My only comment is that putting a amplifier behind this rig is almost useless; these radios have very poor sensitivity. I've been looking for something to improve the sensitivity. The good folks at 4 Square have stated that there is no need for better sensitivity, as it's a QRP rig. This was also noted in the QST review. Thanks again for the video. 73, John W4JPL
It's got plenty of sensitivity for 75 meter AM, especially for our regional nets. The extra power just helps others hear me. There is no way to boost the RX gain due to the unusual RX/TX configuration where the final amp is actually the receiver's front end, very odd. One easy solution is get one of the old Ameco PT-xxxx preamps. It will handle the TR operation plus add some front end gain.
Nice mods Steve. I was wanting to know where you soldered the wire, resistor coming from the PTT to RCA jack? Thank you, Tim
The resistor, 10k or so, goes from the PTT terminal to the base of the NPN transistor. The collector goes to the center pin of the RCA jack and emitter goes to ground.
Don't really know enough about them but does your D104 really still have a crystal element in it? My impression was that they needed an amp circuit in the base to work but it works ok with just the amplification in the N75? Thanks n 73
All of the original D104's were crystal going back to the mid 1930's. The crystal element has a high impedance which works well with tube type amplifiers however solid state radios started showing up in the late 50's and they have a lower impedance input which tends to degrade the low frequency audio response from the crystal element. The work-around was to use a preamp in the base. D104s began showing up with ceramic and dynamic elements. Yes mine and thousands of others are crystal.