Will this work?

This forum is for the discussions targeted at converting various models of Motorola equipment to operate in the 900MHz Amateur Band.

Moderator: Queue Moderator

Post Reply
Jonathan KC8RYW
Posts: 1747
Joined: Fri Dec 28, 2001 4:00 pm

Will this work?

Post by Jonathan KC8RYW »

I sketched up these plans the other night, for a 33cm setup I might make in the future.

Can someone tell me if this will work?

The transmitter frequencies are 125 KHz apart.

My concern is this: the transmitters are really transcievers, except the recieve section isn't being used. But the reciever is still connected to the antenna port via the antenna switching circuit. I assume the InterModualtion panel [isolator, dummy loads] will prevent any RF from the other two transmitters from hitting the reciever, and burning it out? I'd rather be safe then sorry.

A big thank you in advance!

Image
73 DE KC8RYW
Random Motorola Part Number:
SYN1894B - V3m Sprint-branded Battery Cover
User avatar
xmo
Moderator
Posts: 2549
Joined: Fri Oct 12, 2001 4:00 pm

Post by xmo »

Your receive side set up looks fine.

Combining transmitters at 125 KHz spacing at 900 MHz is a problem. Traditional cavity-ferrite combiners like to have 500 K or better spacing. At close spacing the industry uses what is called a hybrid combiner. An example of a suitable hybrid coupler would be a DB4376.

It is possible that your transmitter combining concept may work but I suspect the cable lengths may be critical. If you have access to a VNA you could always set it up and see if it looks like it will work.
Jonathan KC8RYW
Posts: 1747
Joined: Fri Dec 28, 2001 4:00 pm

Post by Jonathan KC8RYW »

xmo wrote:Your receive side set up looks fine.
Sorry, I took this out at the last minute.

I'll add it back in:

Image
73 DE KC8RYW
Random Motorola Part Number:
SYN1894B - V3m Sprint-branded Battery Cover
Post Reply

Return to “Converting Motorola Equipment to 900MHz Amateur”