---------- Original Message ----------

From: JOHN HASERICK <jhaserick84@...>

To: Jon Cunningham <jcunham@...>

Date: 12/29/2024 1:00 PM EST

Subject: Re: wacom 2 meter cans

 

 

Jon, Because the RX and RX frequencies on 2 M are so close , probably the same. I made a mistake- correction is that from the TX connector, best SWR, RL and closest to zero reactance should be on the TX, not RX frequency, and visa versa.

 

John

On 12/29/2024 12:54 PM EST Jon Cunningham <jcunham@...> wrote:

 

 

 

Both jumpers to the T the same length?

On Dec 29, 2024, at 12:24 PM, JOHN HASERICK <jhaserick84@...> wrote:

Hi Jon,

 

A ham club I belong to had a Wacom duplexer for 6 meters that had one of the in between can jumpers removed and an improper length one substituted. The result was a double notch that could not be joined by any combination of tuning the notch tubes. The proper coax length between cans, and between can antenna port and center of antenna port T, is an electrical 1/4 wavelength. You get it approximated by multiplying 1/4 wavelength by the velocity factor of the coax which is 0.66 for RG224 or 0.69 for RG 400 or RG142. Only use these types coax which are double shielded with silver plated copper braid shield.

 

Start with the jumper between each 2 can pair. When the coax is the correct length there will be just one notch dip and the notch depth will be the deepest. Then do the can to T coax. The best check there is with a return loss bridge (or antenna bridge) connected to say the TX can antenna port coax connector, 50 ohm resistive toad to the antenna T antenna port, and the coax jumper connected from antenna T  receive port to RX cans with 50 ohm load to the RX side duplexer RX port. If the RL dip or best SWR occurs below the duplexer RX frequency, the coax jumper is too long. If above, the coax jumper between antenna T and RX cans is too short. 

 

Then do the same with bridge on RX port coax jumper connector, and 50 ohm load moved from RX side to TX side TX port, still with 50 ohm on the T antenna port..

 

John

On 12/29/2024 8:20 AM EST Jon Cunningham <jcunham@...> wrote:

 

 

Wonder if you can help with our dilemma. We bought the cans new back in the 1980's and were using two antnnas....since then we switched to one antenna and the old T connection and cables have been lost. I made a set about 9 inches long and they work but youm can hear the white noise in the signal....how do I calculate the corrext length for these? I assume we would need to retune with the new cables to make things rightt

Jon- K1TP

145.130 in Gloucester, MA

thanks in advance