-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
Yaesu FT-1000MP Mark-V AM, MOD
- Thread starter cbkidd1
- Start date
It's a matter of using a relay to remove AM audio from the balanced modulator and applying it to the gate of the power control transistor in AM. The same idea as the mod for the TS-940S published on the AM Window site. The main difference is in the Yaesu you use an electrolytic to couple the audio to the gate rather than a 1:1 transformer.
ButtFuzz
Anti-BS Advocate ● WO0WOO ● Reverend Doctor
Couldn't one simply purchase a CB for use on CB? I recently purchased a newsed Grant XL in the box for $30 on marketplace. Granted, I had to ply him with $20 to ship it to me, but total investment is $50. About 1/2 hour of my time, I have a radio that is going to sound, arguably, better on AM in the FCC 40 that the Yazoo is ever going to sound.
And for a whole lot less money and frustration.
And for a whole lot less money and frustration.
Once you apply audio to the gate of the power control FET, you are effectively modulating an RF stage in the HF rig rather than an IF stage. The difference in AM audio is dramatic and rivals the best sounding AM radios since this stage has very little bandwidth limitations and strong positive modulation peaks. The results are just like direct injecting audio into the Darlington, series pass modulator on a 148GTL with a lot more power. The spectral purity of that power is also very difficult to replicate with most external amplifiers available in that market.
You could just feed outside audio into this gate through a coupling cap but the radios mic preamp stages have plenty of headroom to modulate this RF stage with good quality audio once you bypass the limitations of the IF stage. The only other parts needed are the relay to switch the audio from the normal path in other modes, to the gate of the power control transistor (one connected to the wiper of the drive, carrier or power control potentiometer) in AM. One small switching transistor keys the relay through a resistor driven from a positive voltage present only in AM, typically found around the AM filter. Use a diode across the realy coil.
If the clean 100+ watts doesn't attract someone to an HF rig, the receivers on some of the higher end rigs like this one will make it so you never want to sit behind a CB again. The dynamic range and filters available in the HF rig make listening a pleasure. It's not that the HF rig will hear things on AM that a good double conversion CB won't. Their sensitivity here is often similar. The difference is the sound quality and the ability to use those filters under different receiving conditions. When the signal is weak, switch to a narrow filter and improve the signal to noise ratio. When the signal is strong, go wide and hear the full fidelity. Notch is great at removing carrier hetrodyne too.
You could just feed outside audio into this gate through a coupling cap but the radios mic preamp stages have plenty of headroom to modulate this RF stage with good quality audio once you bypass the limitations of the IF stage. The only other parts needed are the relay to switch the audio from the normal path in other modes, to the gate of the power control transistor (one connected to the wiper of the drive, carrier or power control potentiometer) in AM. One small switching transistor keys the relay through a resistor driven from a positive voltage present only in AM, typically found around the AM filter. Use a diode across the realy coil.
If the clean 100+ watts doesn't attract someone to an HF rig, the receivers on some of the higher end rigs like this one will make it so you never want to sit behind a CB again. The dynamic range and filters available in the HF rig make listening a pleasure. It's not that the HF rig will hear things on AM that a good double conversion CB won't. Their sensitivity here is often similar. The difference is the sound quality and the ability to use those filters under different receiving conditions. When the signal is weak, switch to a narrow filter and improve the signal to noise ratio. When the signal is strong, go wide and hear the full fidelity. Notch is great at removing carrier hetrodyne too.
Last edited:
Hello Weedhopper. Long time no talk. Hope all is going well with you. That D-201 I purchased from you decades ago, is still on my desk today as a daily talker and I thank you again for that deal
I wouldn't mod it. As will most modern amateur HF rigs AM mode seems like an afterthought. They only sound ok on AM. Where they really shine is on SSB mode. I know, I have the 100 watt version with built in tuner.
I'd say keep it for SSB and buy a cheap cb for AM work if you want to sound like a cb'er.
YMMV
I'd say keep it for SSB and buy a cheap cb for AM work if you want to sound like a cb'er.
YMMV