Repeater Question

Status
Not open for further replies.

stalcupcomm

Member
Joined
Nov 12, 2011
Messages
4
Location
S.C.
I live in the mountains and have a repeater up and running. It is a "home brew" repeater consisting of two 40 watt Motorola GM-300s tacked together with a 50 watt Cellwave duplexer running a 5 MHz split in the VHF band. My question is this, If I were to add a 100 watt amplifier to this system in line between the duplexer and the antenna, will this have a negetive effect on the performance and isolation of the duplexer? If I place the 100 watt amp in line between the TXer and the duplexer, I will have to get a new duplexer as the old one is only rated for 50 watts. Thank you all.
 

loumaag

Silent Key - Aug 2014
Joined
Oct 20, 2002
Messages
12,911
Location
Katy, TX
I have no direct answer to your question, but when approving your post I was curious as to who you were stepping on with a 5 MHz split in the VHF spectrum?
 

stalcupcomm

Member
Joined
Nov 12, 2011
Messages
4
Location
S.C.
According to what is printed on the duplexer, it says the split is 4.020 MHz, so right at 5 MHz split. II new it was close to 5, just couldn't remember the exact numbers.
 

W2PMX

Member
Joined
Oct 29, 2011
Messages
333
Location
Fayetteville NC
To answer the question, you won't receive anything if you put the amp between the duplexer and the antenna. You also won't gain much. 50 watts to 100 watts is only a 3db increase, and considering the capture ratio of the receivers that will be receiving the repeater (I'm assuming they're just a bit younger than I am), that's almost no change at all.

And, if this is being used in commercial service (IOW 152-174MHz) in the US, it's very illegal. Using the two as a repeater isn't type-approved.
 

newsphotog

Member
Premium Subscriber
Joined
Jul 29, 2008
Messages
883
Location
Des Moines, IA
I favor using a better antenna before utilizing amps and preamps. Power isn't everything... antenna height and gain is a lot more.
 

W2NJS

Member
Joined
Mar 27, 2006
Messages
1,934
Location
Washington DC
For whatever reason this post appeared in the Amateur Radio Forum, although the OP is using a 5 mHz offset on, he says, VHF. I too would be curious as to what exactly it is he's trying to do.
 
Last edited:

WouffHong

Member
Joined
Oct 11, 2005
Messages
305
Location
Jawjuh :)
repeater

I have no direct answer to your question, but when approving your post I was curious as to who you were stepping on with a 5 MHz split in the VHF spectrum?
He might have meant UHF, but wonder if the necessary Repeater-Coordination was made?

Da Wouff
 

WouffHong

Member
Joined
Oct 11, 2005
Messages
305
Location
Jawjuh :)
Both??

Should't be "stepping on" anyone. Im Licensed for both freqencies.
If you are not uncomfortable answering: What do mean by that? What frequencies are calling "licensed for both"?? - Ham? Commercial? bootleg? GMRS???The information you give us leaves us with more questions than answers WRT that part.:roll:
 
Joined
Dec 26, 2004
Messages
1,217
Location
Tulsa
According to what is printed on the duplexer, it says the split is 4.020 MHz, so right at 5 MHz split. II new it was close to 5, just couldn't remember the exact numbers.
In the world of duplexers that isn't even close, your performance will be almost non-existant. Pass/reject frequencies need to be tuned to the exact frequencies of the transmitter and the receiver, close only counts in horseshoes, not in duplexer tuning. If you are indeed using this in the VHF commercial band, your license for the repeater output frequency will need to licensed for FB2 or some variant thereof.
 

Kd8kub

Newbie
Joined
Nov 20, 2011
Messages
1
Help

Can someone show me how to calculate losses for a repeater system. What I need to fiquare out is for
LMR-400 coax cable, N connetors and duplexer.

Losses for each is:

LMR-400 is 2.7

RFS Duplexer 633-6A-1N is 1.4 insertion loss

N connectors Not sure.

I need this ASAP.

Please show how to do this. Thanks
 

W2PMX

Member
Joined
Oct 29, 2011
Messages
333
Location
Fayetteville NC
Can someone show me how to calculate losses for a repeater system. What I need to fiquare out is for
LMR-400 coax cable, N connetors and duplexer.

Losses for each is:

LMR-400 is 2.7

RFS Duplexer 633-6A-1N is 1.4 insertion loss

N connectors Not sure.

I need this ASAP.

Please show how to do this. Thanks
You add the losses, so 2.7db + 1.4db = 4.1db. Good N connectors connected properly will run under 0.1db loss each, so you can almost ignore them. (BTW, 3db is half, so you're losing more than half your power.)
 
Status
Not open for further replies.
Top