Meeting Minutes - August 2012
There are no new members with membership standing at 13.
No funds were paid or received during the last month.
Search And Rescue - Amateur Radio Presentation Request
Larry Stokes (N7IBC) reported that a request has been made to present information on amateur radio communications capabilities at a Search And Rescue (SAR) meeting to be held at the State of Idaho Department of Lands building, located at 555 Dienhard Lane in McCall, on the 15th of August at 7:00 PM.
2-Meter and 33cm Repeaters
The membership unanimously voted to approve the move of the 2-meter repeater to the Brundage Mountain repeater site.
The membership unanimously voted to approve the purchase of the two backup Kenwood TK-705D radios for the 2-meter repeater at a total cost of $75.
Ray Montagne (W7CIA) reported that the 2-meter repeater and 33cm repeater are operating correctly. Issues were discovered with the LDF4-50 hard-line and a temporary feed-line was installed between the repeater cabinet and the temporary antenna. Testing of the remaining run of LDF4-50 have not been completed. Should the remaining LDF4-50 feed-line prove not viable then a recommendation for a 50 foot run of LMR-600 (the feed-line needs to be sufficiently low loss for the 33cm repeater - LMR-600 would present a -1.5 dB loss at this length or Andrew CNT600 would present a -1.25 dB loss at this length).
Bob Renn (KF7JPJ) reported on bids for a permanent antenna mounting system for the 2-meter repeater. Concerns were raised regarding the stability of the mounting system with respect to the building structure. An ad-hoc committee will meet at the parking lot that is located approximately 1 mile up Bear Basin Road, from highway 55, on Tuesday, August 7th at 10:00 AM, and will be traveling to Mount Brundage to assess options and formulate a plan for antenna mounts.
Discussion took place regarding options for a smaller antenna. It was thought that a 4-bay dipole was available in the Pocatello region but further investigation showed that the antenna is only a 2-bay antenna.
Ray Montagne (W7CIA) will record equipment manufacturer, model and serial number for the repeater systems.
Ray Montagne (W7CIA) reported that the 70cm repeater receiver front end has failed while the transmitter and duplexer are in excellent condition. Direction was requested regarding options on radio repair versus radio replacement, with the membership favoring radio repair.
Following the meeting, the morning of August 3rd, the receiver front end transistor has been removed from the receiver to determine the transistor manufacturer and manufacturer part number. The device, Repco Dimension™ part number 48-01-062 for transistor Q1, is a Motorola MR5904 (markings are MR5904 312). More than 12 hours of internet searching in an attempt to locate a datasheet / specification for this device has thus produced no results. The Repco Dimension™ repeater is model number 830-250-5, serial number M-F22145, Catalog Number WRN60KD, FCC TX DATA BB3080, FCC RX DATA BB3080. The NPN bipolar transistor device that was removed from the receiver has four leads, consisting of Base, Emitter, Collector and Substrate in what appears to be a TO-72 or TO-18 package.
An evaluation of the receiver front end circuit diagram, which depicts D.C. voltages, shows the transistor to have an hfe of 37.5 (as determined by a collector current of 1637.2 µA ÷ a base current of 43.6 µA).
There is no indication in the Repco Dimension™ manual regarding RF gain. A small signal RF bipolar transistor with an hfe of 37.5 at a collector current of 1637.2 µA and a maximum frequency of 500 MHz or greater, preferably in a TO package, with a low noise figure is required.
Possible candidates for a replacement transistor include:
|Small Signal RF Bipolar Transistors|
|Advanced Power Technology RF||BFY90||20-125||TO-72||2.5 dB @ 500 MHz||1.3 GHz||$4.51|
|Advanced Power Technology RF||MRF904||30-200||TO-72||1.5 dB @ 450 MHz||4 GHz||$5.46|
Larry Stokes (N7IBC) has a 70cm Motorola GR-1225 repeater that has one channel slot programmed with the KC7MCC 70cm repeater pair and has offerred to loan this repeater to CIARC in order to secure access to the No Business - Midway Peak radio site. Ray Montagne (W7CIA) is installing a 33cm link radio into this system. If this system is to be installed at the No Business - Midway Peak radio site, the CIARC 70cm duplexers will be installed so that Larry's duplexers will not need to be re-tuned.
Martin will be calling regarding the No Business - Midway Peak radio site to setup a meeting to determine if CIARC will be allowed to install the 70cm repeater. Ray Montagne (W7CIA) will send an email notification to the club members when this meeting is scheduled so that interested parties can attend. Ray will also prepare block diagrams of the repeater system for that meeting.
A request was made that Larry Stokes (N7IBC) contact the parties from Nevada that were present at the Idaho convention in April, and sold the 2m isolator to CIARC representatives, to determine if they have a 70cm isolator for sale. Requirements for the 70cm isolator are:
The isolator must be tunable, with the CIARC transmitter frequency of 442.500 MHz falling within the range of tuning adjustment.
The isolator should have two ports. If a two-port isolator is not available but a single-port isolator is available then the single-port isolator should be procured.
The isolator should have a 50Ω load with a minimum rating of 50 watts. If the load is not sufficiently rated, this should not block purchase as CIARC can obtain a higher rated load from other parties if necessary.
Ray Montagne (W7CIA) also recommended acquiring a low noise amplifier (LNA) from www.downeastmicrowave.com for $75 (model L432LNA-2N assembled). These LNAs provide +17dB gain with a very low 0.5 dB noise floor. Without the LNA, and assuming that the Repco Dimension repeater receiver can be made to make the manufacturer specification of 0.35 µV for -12 dB SINAD, the losses in the duplexer would degrade the receiver to 0.42 µV for -12 dB SINAD. Installing the LNA would increase the receiver sensitivity to 0.11 µV for -12 dB SINAD and with duplexer losses, this would be degraded to 0.13 µV for -12 dB SINAD, resulting in a very hot receiver.
Other Business - Club Radio Inventory
The membership unanimously voted to approve the sale of existing radio inventory, including the TAIT repeater, to generate funds for the purchase of radio gear for members.