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Hello!
why do you want to use a valve? its old Technology, radios and TV used it, am sure it will work in your case. Though valves are prefarably used in high power circuits at microwaves.
search it in old magazines issues such as elektor etc, old service manuals for radio just check around the mixer stage in radios it is for down conversion , similar you can build for up conversion !
thanks for replies
rf output transistors at 179mghz not exist for public why i don.t know
and it is illegal to get it from out the country without permission
is this rules exists in any place?
so i built a transmitter with a low power about .5 watt
and i want to increase it
i seen through the net many ideas but all around short waves
i have many valves of af output i mean audio
is this suitable for 180 mg hz and also i have valves
for mixer and if all for old radio and i have schematics
so it is easy to get it.s pins and requirment
i guess
it is hard to get some body did that
any way thanks again
i will try
regards
I see that you have a serious motivation to use valves for a VHF amplifier. Basically this should possible, but I'm not sure which types would have a considerable gain at 180 MHz. I know the usual audio amplifier valves (still used for guitar amplifiers) well perform up to SW band. However, with valves you must consider general restriction not known from semiconductors (they have other restrictions in high frequency properties of course), that's electron time of fligth. For this reason VHF and above valves have special construction.
I have an old Valvo (Philips) pocket guide, where a lot of industrial RF and transmitter valves are listed, covering the VHF and UHF bands with up to several 100 Watts. But I have no detailed data or circuits. But I'm sure that amateur radio guys will know better, particularly older guys that may have build and operated VHF and UHF transmitters with valve power stage.
It will depends of output power that you want. You can use 4CX250B (from Eimac), in Class C polarization. You can take the datasheet in **broken link removed**.
How you can see there, it's necessary 1.7W in input to take 235W output power, and you should supply the plate tube with 1k5Vdc.
There are s lot of sites on the web, with schematics and mechanical construction instruction, that describes a PA using this tube for 2 meters band. With a little adjustment in load and source matching circuits, you can do it work in 177MHz.
use a solid state pa valves have a shelf life
transistors last a longer time by far
it depends only on the duty cycle of the amp
is it on more than 50% of the time it lasts
valves wear out in 25% of there expected life most often at least 500% less time than a faulty transistor ...!
becouse makers quote perfect conditions as the norm for valves
transistors are far more reliable when balanced and cooled
and keeping FM broudcast on the air means having a backup unit
anyway
so it evens out but not in cost
valves are cheep for now like desil but transistors are smaller to produce more power now
and many get left behind and not looking at modern stuff
only valves and strip line
i think look at the newer rf stuff made up
ask a makers view {phone the maker of a device and ask for the technical dept}
valves is great for many applications
for accuracy yes 180mhz should have special
valves but i think the valve have agood
specification it is like fet transistor
have no internal connection betwen plate, kathod and grid
sure during works we shoud know it is requirement
to work with vhf it is critical i seen
transmitter in sw through net about 3.5 mhz untill
7 mhz design not critcal coz of frequency
i.ll use audio autput valve
with amplifer class c with smoll transmitter
from transistor but now i.ll search about some information
about capuling betwen the 2 unit.s and the output
requrmint the impedance and the v.peak to peak
of signal which feed the out put unit if any one know document
or link please write
i heat try and error way
i.ll have to use it in small range as i can
and i.ll put result here
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