Minipa70 HF Amplifier Kit New Keying Circuit Part 5
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- Опубліковано 2 тра 2021
- Here is a video on how to make the keying circuit • How to Build a Simple ...
You can purchase this amp kit here amzn.to/3gTd1dM
When looking around I could not find any good video's on how to put one of these kits together so here is a video of me doing one step by step hope this helps everyone out.
![Gatekeeper In Amp Building Concepts - RF Keying Circuit - [For The Layman]](http://i.ytimg.com/vi/imMG94fOEVY/mqdefault.jpg)
What I like about what you did in this kit is you showed what whet wrong as well, that has got to be a good thing. Everyone makes mistakes, but few will admit it.
Is that really not holding latched when it should be. However, that is a simple idea to make it happen.
Thanks for the videos on this amp. I picked one up at a hamfest (already built & supposed to work) so this gives me a good reference when I set it up to use with my QRP rig.
thanks for sharing this great idea. Just curious, can i add an on/off or toggle switch in the circuit to make the rf signal bypass the amplifier without dismantle and reassemble the coaxial cable?
12:34 what are parts the switch you made for turn on relay.
I enjoyed your video series on this linear. Going through the comments I get a piece here and there of your addition. What would really help is a schematic of how you wired in the additional components. Just show it in a video and I can pause it and take a screen shot. Thank you.
Are you talking about the keying circuit if so I will see what I can do about drawing one up for you and making a how to video on it.
@@TheElectronMan I drew out the circuit as best as you described ua-cam.com/video/21za7RDHa8w/v-deo.html
I'm new and trying to build this amp, where is the best place to place the volt meter probes when setting the bias adjustment?
The down and dirty way is to hook it up to the pad on the input transformer and set for around 3.8 volts. Generally the bias is not set as a distinct votlage on the gates. The best way is to set it by measuring the drain current for the two mosfets. The correct current is in the range of 100-300ma per MOSFET for best linearity.
Great video series, been following every video when assembling my own amplifier. Is the transistor's emitter connected to ground and the base to the capacitor? Does the collector go to the pin on the relay? Thanks!
Cool fun project.. Yes the collector goes on the relay and the emitter goes on the ground and you want your capacitor to bridge across the emitter and collector with the neg side of the cap to emitter. The base of the transistor is where your RF input signal will go through using the ceramic cap.
@@TheElectronMan RF is AC, so it will not see the Cap. It is a simple way of doing it :-))
AC waveform Numnuts! DOH!
@@BoB4jjjjs True I am using the cap to smooth out the waveform so there is no jitter in the relay without it you can hear the jitter which is the ac pulsing on the transistor so basically I am just smoothing out the AC pulses with the electrolytic cap at least that is the way I understand it.
@@TheElectronMan It was nice to see you do the build. Any RF projects are good, so if you feel like building any kits please do so and record them. I will be watching.
what are the values of the things that you add?and whats the schematic of the things added.....thank you 73,iz5109swl Florence
You just need a 2N2222 Transistor 10 picofarad capacitor for the RF sense input on the base of the transistor and I used a 470mf cap to control the relay chatter..
I've built this amp. Attached it to a heatsink yesterday. Your keying circuit is inspired. I was wondering how to effect activation... Last thing... Low Pass Filter? What's the deal? Is this amp usable without a filter, or am I going to cause a whole load of trouble for myself and others? Thanks v much. Best, Nick
Thank you I put mine a spectrum analyzer and it is surprising pretty clean with no filters harmonics are not bad at all I would trust it but there are several easy to build filters if yours is not as clean. If I built another I would just use the jumper port for TX to connect my keying circuit and not use the pin on the relay just because it would be a cleaner and effectively do the same thing.
@@TheElectronMan Ok. Understood re: harmonics. Very positive. I'll look at filter circuits anyway. Re: keying circuit off the jumper. How exactly would that be wired up? (Sorry to be dumn). Thanks, N
@@NickRedmayne IF you notice on your kit there is a PTT jumper, instead of lifting the ground on the relay like I did you could just use the PTT jumper as latching circuit just cleaner looking using the PTT spot on the circuit board. It would wire up the same the RF input on the transistor would still be same and the other two connections would go to those PTT pads hopefully that makes sense :)
@@TheElectronMan Thanks. Roger that. So, leave the relay fully seated and instead make that connection on one of the PTT pins, leaving the jumper closed and in place. T'other connection to central pin of SMA?
@@NickRedmayne Close basically you are doing the same thing as the relay connection you are using the transistor to sense the RF and close the circuit but now you are using the two pads where the PTT jumper went as your switch. So you would hook up the two wires that went in-between the pad and ground on the relay to the two PTT pads so when it senses RF it closes the circuit which would be the same as putting the jumper in to activate the amp just now it's done electronically.
Where can I get a copy of that schematic?
I got mine from here iu3idf.blogspot.com/2017/04/a-small-power-amplifier.html
Please provide the schematic for the keying circuit.
Check out my other videos. I have a video dedicated on how to make a keying circuit.
@@TheElectronMan Thanks. Found it. Additional question. When winding the wire through the choke, I damaged the coating on the wire and exposed the copper in several places. Does that wire need to be replaced for the amplifier to work properly?
@@chuckatkinson6728 I would replace it because if the bare parts touch each other the inductance will be off, could cause it to not operate correctl., You can use insulated wire to replace it just make sure it's the same gauge.
Why not just use the key line on your radio - very simple !!!!!
That is actually is what it was designed for if you wanted to run hardwires to your radio.... What I made was a RF sensing circuit so it was not radio dependent but you are correct that could easily be done as well.
@@TheElectronMan The radio key line would be much more reliable !
@@rickmckee6698 I don't disagree just like a foot pedal key is even better and it saves the relay but for portability the RF sense is the way to go that is why most amps have a RF sense keying circuit.