Spitfire Mark 2

[Slim Pickins]

Anyone have one of these rigs? I know they are 23 ch am but that is about it. I know where there is a few that a guy is thinking about parting with and I am wondering if this might be a good first tube radio. Is there any way to add the upper channels to make this a 40ch rig? I have never had a tube type radio before but I find the old technology to be appealing. What would be a fair price for one in decent working condition?

73s
Paul

[Slim Pickins]

OK, I picked one up as a bonus with another radio I was getting. It is built by Cardon and comes with what looks like the stock mic. It powers up and all the tubes light up. The meter sticks a little and was going all the way up when I turned on the volume from standby. There is a meter adjust knob on the back and when I turned it the meter fell but I don't know how to accurately calibrate it. There is also adjustments on the back for Load and Plate. I have no idea what these do so I left them alone. When I key the mic the meter swings backwards now that it is only sticking a little. This radio should work on my regular cb antenna, right?(I have a .64 groundplane). When I checked the radio with my swr/power meter it showed nothing. Will a regular meter work with these type radios? I got it thinking it would be a good project to play around with and see if I could get working right.

Here is a pic
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Thanks for any help
PAul

[Night Crawler]

You'll need a signal generator with an adjustable output to calibrate the S meter.
The Plate and Load is for tuning the Final Amplifier.
If it's a cb it will work with a cb antenna and it will work with a regular swr/rf meter.

[Slim Pickins]

Thanks Night Crawler,

I had it hooked to my antenna after making the last post and it seemed to have decent recieve. I was worried about keying it up without knowing everything will work. When I first plugged it in when I brought it home I had it hooked to my antenna through my swr/watt meter but my meter did nothing, I tried it on Cal first to calibrate the meter so I could check the swr. Turned the calibration knob on the meter all the way and no change in the needle. Seems like it is not actually putting anything out for the meter to measure.

73s
Paul

[Slim Pickins]

You'll need a signal generator with an adjustable output to calibrate the S meter.
The Plate and Load is for tuning the Final Amplifier.
If it's a cb it will work with a cb antenna and it will work with a regular swr/rf meter.

Is tuning the plate and load something I can do myself? If given the information I need to know to do it I mean.

[Night Crawler]

The proper way to do it is to use a plate current meter in series with the B+ line going to the plate of the final amplifier.

Then transmit and dip the plate control for a minimum reading on the current meter increase the load then dip the plate current again with the plate control.

Work them back and forth until the correct plate current is showing on the meter for the mode of operation that will be used.

The plate control should be the last one adjusted for a minimum reading on the current meter.

The easy way to do it would be to just use a watt meter and tune the plate and load for a maximum reading on the meter.

When tuning use the antenna since the plate and load are part of a PI-network and will match the output impedance of the transmitter to the load or antenna usually within a range of 25 to 100 ohms.