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THE AM BULLETIN BOARD => Technical Forum => Topic started by: NR5P on March 28, 2012, 11:57:47 AM



Title: Gi-7b plate modulated?
Post by: NR5P on March 28, 2012, 11:57:47 AM
This is one of those Russian coaxial tubes. I have some of them and trying to find any that have been used for class c. Besides mounting and neutralization are there any issues with putting these tubes in am service? http://frank.pocnet.net/sheets/018/g/GI7B.pdf


Title: Re: Gi-7b plate modulated?
Post by: KM1H on March 28, 2012, 12:47:20 PM
Id start by hi potting to see what HV headroom you have and then plan accordingly.

Carl


Title: Re: Gi-7b plate modulated?
Post by: kb3ouk on March 28, 2012, 06:50:44 PM
According to the datasheet, those things are microwave tubes, for use at centimeter wavelengths. Don't know how well one would work at HF. Might be a good tube for VHF or UHF though. Wonder if anyone ever tried AM on the 70 cm band?


Title: Re: Gi-7b plate modulated?
Post by: NR5P on March 28, 2012, 07:20:55 PM
There are a lot of them as linear amplifiers.  Mostly people modify existing amps and swap these in.


http://gi7b.com/

and

http://gi-7b.com/

Plus side is these tubes are dirt cheap on ebay


Title: Re: Gi-7b plate modulated?
Post by: w4bfs on March 28, 2012, 10:12:22 PM
negative side is that sockets are hard to find and not cheap


Title: Re: Gi-7b plate modulated?
Post by: NR5P on March 29, 2012, 05:14:25 AM
I've got the tube socket covered. I was going to build a linear amplifier but I hardly use sideband. I've always wanted a high power plate modulated transmitter and I got one of those big heavy duty metal cabinets for free. I need to start filling it. I'd have to make up for the lack of glow with nice modulation tubes. Maybe trying to do something that isn't well documented is over my head.


Title: Re: Gi-7b plate modulated?
Post by: KM1H on March 29, 2012, 12:05:43 PM
Quote
According to the datasheet, those things are microwave tubes, for use at centimeter wavelengths. Don't know how well one would work at HF. Might be a good tube for VHF or UHF though. Wonder if anyone ever tried AM on the 70 cm band?

What does its frequency range have to do with anything? All that sets is the upper limit and the tube could be used at DC or audio if desired. There are numerous UHF capable tubes in use at HF already.

The GI-7B would likely be a better AM tube than SSB since its IMD performance is not very good.

Carl
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands