Transverters

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StormShadow
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Transverters

Post by StormShadow » 29 Oct 2015, 18:50

Hi I don't know to much about transverters but hoping somebody can tell me a bit more on how they work.

I have seen some transverter boards that I'm thinking of getting to convert a couple of old SSB 11 meter radios. I've never used a transverter before so I don't know how good they are. The ones I have seen and want to get are for 6 and 4 meters, so its 28MHz in and 50MHz - 52MHz out and 28MHz in and 70MHz out

So the 4 meter band is 500 KHz wide so does that mean that the CB radio has to be 500 KHz wide at 28 MHz? so 28.000 MHz - 28.500 MHz?

6 Meters is 2MHz wide, would that mean the CB radio has to cover 28 MHz to 29 MHz?

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Re: Transverters

Post by Auldgeek » 29 Oct 2015, 21:45

That's the general rule.
28.000-28.500 = 70.000-70.500
You will find most 6m activity is 50.000-50.500 so unless you intend to use FM, you only need the 1st 500khz of the 28Mhz band.

One thing to watch is drive power. Most transverters only need a few hundred milliwatts for full output so ensure your TX power is well attenuated.
RX gain is also usually quite high so really useful if your 28mhz radio has a variable rf gain.

Good luck with your project
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I've changed radios that many times, I've forgotten what I have :think:

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Re: Transverters

Post by StormShadow » 30 Oct 2015, 21:38

Awesome I thought so but wasn't 100% so I thought I'd ask... well that makes things a lot more simplified. Its given me some ideas to build some transverters to to run from 27MHz for some HF bands to make some other time. I've found some good schematics online. My first project will be the 4 meter transverter.

Many thanks for the info

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Re: Transverters

Post by HFDX » 31 Oct 2015, 19:59

I use transverters on 4m, 23cm and 3cm. They up-convert and down-convert all the modes that your driving transceiver have. So in your case, as you only have an SSB driver, you only need to cover the SSB sections on 6m or 4m or 2m ... ie about 500kHz worth. Convert your 11m set to 10m, ideally 28.0 - 28.5MHz, ... most transverters accept milliwatts of drive .... up to 5W (depends on model etc) ... so make sure the driver matches the transverter drive power. If youre modding an 11m rig you might be able to find a point in the Tx chain immediately before the PA transistors where the drive power is low enough. Regarding 4m --- you will be very disappointed with performance if you dont use a proper (Yagi) antenna ... operating on SSB will require a horizontally polarised antenna ... at 6m / 4m ...and, as the transverter is low power, you will struggle (unless its via Sporadic-E during the summer). For normal tropo you will be disappointed. Maybe start with a 2m transverter where activity is higher and a small Yagi will give better results but you will probably need to bolt on a small PA after the transverter to give a few watts output, although some transverters do give 10W/25W depending on model. Personally I wouldnt start on 4m (which by the way is my band of choice) .

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Re: Transverters

Post by StormShadow » 31 Oct 2015, 22:56

Do you get much on 23cms and 3cms? I'd love to do some experimenting in those bands. I'll be running FM and AM as well as SSB but I'm not sure in the way of how transverters work whether you'd need extra mods involved or not, I maybe wrong but lets say I've got a CB radio that I've converted to 28 MHz to 28.500 MHz to use on 4 meters and it does all modes, then the modes will be the same right on the output of the transverter at 70 MHz to 70.500 MHz with the right KHz steps in between appropriate for the 4 meter band right? I'm aware that transverters only except milliwatts of power at the IF. I use a 4 meter dipole thats very high up, It was vertically polarized but recently its sorta moved in between horizontally and vertically polarized so its in between. The circuit diagrams I've looked at shows that I'll need to build the finals but thats not a problem I can make those too. I enjoy making things. I'd like to learn a bit more from you in the way of transverters I'm only just beginning to understand them :)
HFDX wrote:I use transverters on 4m, 23cm and 3cm. They up-convert and down-convert all the modes that your driving transceiver have. So in your case, as you only have an SSB driver, you only need to cover the SSB sections on 6m or 4m or 2m ... ie about 500kHz worth. Convert your 11m set to 10m, ideally 28.0 - 28.5MHz, ... most transverters accept milliwatts of drive .... up to 5W (depends on model etc) ... so make sure the driver matches the transverter drive power. If youre modding an 11m rig you might be able to find a point in the Tx chain immediately before the PA transistors where the drive power is low enough. Regarding 4m --- you will be very disappointed with performance if you dont use a proper (Yagi) antenna ... operating on SSB will require a horizontally polarised antenna ... at 6m / 4m ...and, as the transverter is low power, you will struggle (unless its via Sporadic-E during the summer). For normal tropo you will be disappointed. Maybe start with a 2m transverter where activity is higher and a small Yagi will give better results but you will probably need to bolt on a small PA after the transverter to give a few watts output, although some transverters do give 10W/25W depending on model. Personally I wouldnt start on 4m (which by the way is my band of choice) .

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Re: Transverters

Post by GeeFull » 01 Nov 2015, 08:10

StormShadow wrote:Do you get much on 23cms and 3cms? I'd love to do some experimenting in those bands. I'll be running FM and AM as well as SSB but I'm not sure in the way of how transverters work whether you'd need extra mods involved or not, I maybe wrong but lets say I've got a CB radio that I've converted to 28 MHz to 28.500 MHz to use on 4 meters and it does all modes, then the modes will be the same right on the output of the transverter at 70 MHz to 70.500 MHz with the right KHz steps in between appropriate for the 4 meter band right? I'm aware that transverters only except milliwatts of power at the IF. I use a 4 meter dipole thats very high up, It was vertically polarized but recently its sorta moved in between horizontally and vertically polarized so its in between. The circuit diagrams I've looked at shows that I'll need to build the finals but thats not a problem I can make those too. I enjoy making things. I'd like to learn a bit more from you in the way of transverters I'm only just beginning to understand them :)
If you transvert from 28 to 70 MHz, its a direct conversion.
You are simply adding on TX, or subtracting on RX, the transverters local oscillator frequency and the radios actual tuned frequency, in the case of 28/70 transverters, 42 MHz!

70 minus 28 = 42.

Also, whatever "steps" are available on the prime mover radio, are exactly "mirrored" by the tranverter, albeit shifted up in band frequency.
IE 28.000 Mhz = 70.000 Mhz, and move the radio say 10 KHz and you get 28.010 MHz = 70.010 MHz.
The FM channels on 4 metres are 12.5 KHz spaced, CB's in general have 10 KHz channels, so you will need a bit of "shift" on the radio to get them all exactly, some will line up of course.

Whatever modes are available on the prime mover radio, are of course also available on the new transverted to frequency.
Just for interest, if converting the CB radio you intend to use for transverting from is a pain/problem from 27 to 28 MHz, you can always replace the local oscillator xtal in the transverter from 42 MHz, to one of 43 MHz, and leave the radio on 27 MHz!

(I did similar to that years ago, when I knocked up my first 50 MHz transverter from a kit, and used an old UK FM CB I had lying about, to give me 6 metres FM.
And as by fortune the FM channels on 6 metres are also in 10 KHz steps, it worked out perfect to give me a chunk of the 6 metre FM portion! :D)

The maths is very simple:

Required operating frequency minus radio frequency = local oscillator required.

For 27 MHz exactly: 70 MHz minus 27 MHz = 43 MHz.

And if the CB is stuck on standard channels and doesn't do "the zero's", IE its prime channels end in a 5, that will need to be taken into account when choosing the local oscillator xtal frequency, to compensate.

IE Radio actualy starts at 26.965 MHz, you want that channel 1 to be 70.000 MHz exactly, then 70 minus 26.965 = 43.035 MHz for your local oscillator xtal.

Obviously it makes life easier if the CB radio can be shifted to the "zero's" and start on a whole number ie 27, as this means whole number, often off the shelf, value xtals!
With a continuous VFO type prime mover, lets say an old Belcom LS-102, another radio I often transvert from, its not a problem of course, as you simply spin the dial, and transvert continously without having to take radios fixed "channels" into account.
Hope any of that helps.

BTW there is nothing illegal about this, transverting from a CB frequency to an amateur frequency, as the radio's operational frequency band is only providing the first IF of the system, many amateur radios have oddall first IF's that are none amateur related frequencies!

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Re: Transverters

Post by StormShadow » 02 Nov 2015, 16:58

Many thanks for the info, very useful information there. I'm looking forward to making my first transverter, as this one will be my first build I'll keep it simple, it will be for 6 meters FM for now. I have chosen a CB radio to convert which is a UK 40 Channel FM rig with blown RF outputs so that will be perfect for my project :D so I'm going to go for 6 meters FM simplex for my first build.

I'm planing on making 4 transverts in total. So I will make on for that FM 40 CB radio
I'll make another for 4 meters for an AM FM CB
I will also make a 6 meter one for all Modes
I will also do a 4 meter one for all modes

So this is what I'd be hoping to get:
Harrier CB - 6 Meters FM
Murphy CB - 4 Meters AM/FM
Ham International Multi Mode 2 on 4 meters USB/LSB/AM/FM
Ham International Multi Mode 2 on 6 meters USB/LSB/AM/FM

Your probably wondering why I need so many, I think its cool to have a collection of old CB Radios on Ham Bands :D Can't beat the old classic look.

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Re: Transverters

Post by zippy » 03 Nov 2015, 15:57

Hello, if you use a MM2 then you will suffer from the 5 alpha channels being missing per bank and channels 22-26 going mad. I would recommend a 5555 variant so as you can program sequential channels to be converted, you can tailor the host radio to match the transverter rather than vice versa. you will also have a reference frequency readout rather than conversion charts galore.
If you can only use an MM2 then a simple n converting eprom or pic would be beneficial.
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Re: Transverters

Post by StormShadow » 14 Nov 2015, 05:28

I already have an Anytone AT6666 but I don't really like it much, I might get the 5555 and see what thats like, I like the idea of programming it to frequencies to run a transverter... I've never programed a Anytone 5555 radio before. Can you program the RF power levels? a transverter or the one I'm making can only take around 100mw to drive it, thats the only problem, unless I can find another schematic :idea:

I have thought about making a dual bander 6 & 4 meters, an Anytone 5555 would be good to drive something like that but anyway thats just an idea for now.

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Re: Transverters

Post by GeeFull » 14 Nov 2015, 10:34

StormShadow wrote:I already have an Anytone AT6666 but I don't really like it much, I might get the 5555 and see what thats like, I like the idea of programming it to frequencies to run a transverter... I've never programed a Anytone 5555 radio before. Can you program the RF power levels? a transverter or the one I'm making can only take around 100mw to drive it, thats the only problem, unless I can find another schematic :idea:

I have thought about making a dual bander 6 & 4 meters, an Anytone 5555 would be good to drive something like that but anyway thats just an idea for now.
The power input to your transverters could be attenuated if the radio you use can only be reduced to an amount larger than the required 100 mW.
Microwave modules used to do inline attenuators for their ranges of transverters, my 23 cms variety came with one for use on 2 metre sets that exceeded its 0.3 watt maximum input, (15 dB attenuator allows input of 10 watts max when inline), for that very reason.
Obviously still pays to run the radio on the minimum you can get it down to, as there is no point dissipating loads of RF as unwanted heat in the resistive inline attenuation network.

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Re: Transverters

Post by Maple » 14 Nov 2015, 10:58

There is also a thread about converting a Lincoln. Maybe you're interested.
http://www.transmission1.eu/viewtopic.php?t=31774
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Re: Transverters

Post by slamjam » 15 Nov 2015, 11:41

be careful with using a CB as a driver for a transverter - there is the issue of ptt switching, most transverters do not use rf switching. The other thing to be careful with is drive level. Most use a few milliwatts drive so you will either need to reduce power internally or to add an attenuator and sutiable switching after the radio.
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