[K3CAL] K3CAL Repeater System Status as of Apirl 6th 2024

[KB3WFV]

All,

Here is the current status of the K3CAL Repeater System.

146.985 SUNDERLAND: 
This repeater continues to unfavorably react to other transmissions from other equipment in the Sunderland Shelter. This interaction has plagued the 146.985 for many years. While the new tower site with the new circulator-isolator and associated filters has help to minimize the interaction, it has not been completely resolved. Over the past year the 146.985 repeater wil fail into an open squelch condition with a bouncing courtesy tone. In addition, weak signal station received by the 146.985 will have a noticeable noise increase on the  transmission. In some cases the weak signal station can be cut off completely. The open squelch, courtesy tone and noise all coincide with transmissions of other systems at the Sunderland site occurring at the same time as the  146.985.

On Saturday March 23, 2024, and again on Monday March 25th. Matt N3IVK and I visited the Sunderland Site.
Testing of the 146.985 system has found the circulator-isolator is attenuating the 146.985 TX signal by almost 50%. The dummy load on the side of the circulator- isolator is getting hot. Testing revealed that it is dissipating as much as 3.2 watts. It was also observed that the DR1x repeater is hearing it's self, at least according to the LED status indicators on the Arcom RC210 controller.

The above indicates that the isolator- circulator needs to be replaced. It also indicates a problem with the duplexers and, or a possible problem on the tower. However the 146.985 duplexers are old and have been adjusted multiple times. Some records indicate that the duplexers have been adjusted at least FIVE times by several different people. The were purchased used to begin with and moved several times, from Sunderland to Prince Fredrick. Even a stop at the Hospital before being move back to the Sunderland site. Records also indicate that one of the cavities is difficult to tune.

April 5th 2024: The isolator-circulator is the property of Calvert County and therefore CARA is not responsible for it's replacement or repair.  Shawn N3AE visited the Sunderland Tower Site and removed the 146.985 isolator. Bill N3XMZ  delivered it to the Calvert County radio shop, they will order anew one.

Regarding the Duplexers: The consensus is that CARA should replaced them. Many of you may recall that CARA replaced the duplexers on the Lusby 444.950 70cm repeater in 2022. Those duplexers were  a $2,700.00 new purchase from Telewave and paid for with donations to CARA. We will have to do the same again for the 2 meter repeater.

Dave W3PQS has secured a quote from Telewave for replacing the Sunderland 146.985 2m repeater duplxers. Telewave has recommended the TPRD1556 duplexers. With a 25% discount  off of list price, the new duplexers will cost CARA  $3,936.64 plus shipping.

The 146.985 repeater remains on the air and is functional. However, it may exhibit different behavior with out the isolator. IE interference, noise, dropouts etc.


444.950 LUSBY: 
An antenna problem was identified in May of 2023. Still waiting on the county to replace antennas.

On April 5th 2024. Bill was able to confirm that the replacement antennas for the 444.950 Lusby tower site have arrived.  The county will work on getting both the antennas and the jumpers to both antennas replaced.

The 444.950 repeater remains on the air and is functional. However, it continues to exhibit behavior consistent with the symptoms of damaged antennas.. IE weakening TX signal, interference, noise, dropouts etc.

The signals from both repeaters are slowly deteriorating. In other words the identified problems appear to be getting worse. Trying to avoid shutting off both repeaters to protect the CARA transmitters and amplifiers from unnecessary damage.

Further information will be passed along as it becomes available.

Brian
KB3WFV