Ridiculously easy 70 CM Ground plane antenna

ri·dic·u·lous

rəˈdikyələs/

adjective. deserving or inviting derision or mockery; absurd. 

1. "when you realize how ridiculous easy to build this antenna is, you will have to laugh"

This antenna I threw together with a bunch of stuff I had lying around. I measured under 1.1 swr on 70cm and pumped 40 watts into it for some test transmissions. 

Materials:

BNC solder on bulkhead connector

ring lugs

solid copper wire. I used 14 guage romex

I used this online calculator to get the length of the quarter wave whip and the radials

http://www.csgnetwork.com/antennagpcalc.html

shove the ends of the ground plane elements into the ring lugs.

solder the radiator into the bnc center pin

I cut everything long and trimmed them to adjust the swr.

the radiating element I bent into a loop to hang the antenna and just kept winding it until it tuned down the the frequency I wanted.

Portable Repeater Project

I'm building a portable uhf repeater.

RADIOS
I'm using a CDM750   CDM1250 as the receiver, and a CDM1550LS as the transmitter.

I used this as a base for the link between the two radios.
http://domtoren.com/990/Bi-_or_Uni-directional_Repeater_cable_for_CDM_type_radios.pdf

When I built it as he described, the transmitter would stay on until I unplugged the repeater cable.
I made a unidirectional repeater with a dedicated transmitter and a dedicated receiver.
I put PTT(TX pin 3) to COR(RX Pin 8) and speaker (RX Pin 11) to mic in(TX Pin 2).
edit: RX pin 14 set to Aux control 1 (config 20000ms duration id 9999)
plan for tx pins to channel steer to high power. external switch selectable to channel

Post taken from http://batboard.batlabs.com/viewtopic.php?t=110880

"Basically, the Channel Select 1, 2, 4, & 8 labels are the binary equivalent of the decimal channel number. 

C.S. 1 active low sends it to Channel 1 in the list; C.S. 2 sends it to Channel 2 in the list, C.S. 1 & 2 togeter sends it to Channel 3, etc. 
I think it works out that if none of the Channel Select lines are active, then the front panel has control of the channel; "

One accessory connectors I salvaged had some jumpers from  Ignition control(Pin 10) to ground, but the other I put to pin 4 (alarm) as Nand described.

Eventually, I could use channel steering to add features or perhaps hard wire in the channels so it would be nice to leave a as many data i/o's available as possible.

Edit:
I changed the mic gain from 3dB to 13.5dB for the transmitter. I programmed two xts3000 radios on the repeater with the ability to go to simplex on the output of the repeater. I noticed the audio was louder on simplex, so I adjusted the accessory mic gain up until the audio sounded the same on simplex vs though the repeater. For me it was 13.5 dB from the Nand's recomended 3dB.

DUPLEXER
I've gotten my hands on an older uhf duplexer, but it's rather large. I have yet to tune it.
I took half of the duplexer off to save on space and plan to use only two of the four cans. they are tuned and operational.

ANTENNA
I'm looking into this roll up j-pole for the antenna
instructions:
http://www.namebrandhandle.net/amateur-radio/howto/rollupj.shtml
calculator:
http://www.m0ukd.com/calculators/slim-jim-and-j-pole-calculator/

wacky colinear antenna plans
http://www.dstar101.com/2m%20and%2070cm%20Colinear%20Flowerpot%20antenna.htm

edit: built a ground plane antenna
http://kk6afg.blogspot.com/2015/06/ridiculously-easy-70-cm-ground-plane.html

BONUS
I'd like to implement MDC1200, as I have a number of uhf XTS3000 that can work with the system.
it would be fun to have names for each radio.

edit info on receiver:
http://www.rayvaughan.com/recall.htm
I hope to have mdc 1200 selectable power output on the tx.
I might have to change the cdm750 out for a cdm1250 reciever.

stuff on motorola
http://batboard.batlabs.com/index.php

update #1
http://kk6afg.blogspot.com/2015/06/repeater-project.html