Operating Position
It is possible to operate the Palomar 90A Amplifier in any position. However, since there is no forced-air cooling, we recommend that the amplifier be kept upright on the feet provided on the bottom cover. This allows air to flow in the bottom and around the power amplifier tubes, carrying the heat away through the holes in the top cover.

NEVER set the amplifier on top of other equipment; doing so would allow preheated air to enter the bottom of the Palomar 90A Amplifier. Do NOT operate the amplifier in a small, confined space where there is no continuous supply of cooling air. In other words, keep it out of small closets, desks or similar confined areas. If handled properly, the amplifier should give long, trouble-free service.

Connection
All connections are made to the rear of the amplifier. Connection to the driver or transceiver is made using RG58AU or RG8U 50 ohm coax. The connectors on the amplifier are 50239 coax connectors. The mating plug on the coax cable is a PL259 coax connector and can be found at most radio supply houses as an off the shelf item. When buying coax, it is advisable to pay a little more and get a good grade coax with a tightly woven shield. Low grade coax has poor shielding and may even cause a bad match between driver and amplifier as well as between amplifier and antenna. Coax from the Palomar 90A Amplifier to the antenna should not be smaller than RG8U. You will find that smaller coax will be warm to the touch after long AM transmissions, indicating losses in the smaller cable.

On the rear of the amplifier will be found a place to attach a ground wire. We strongly recommend a good ground connection to this point. It prevents shock hazard when touching any of your equipment, increases the efficiency of your antenna system and minimizes TVI problems. Attaching to a water pipe is not necessarily a good ground if it is several feet from the point where the pipe goes underground. It could be some resonant length that would look like a poor, or no ground at all, at some operating frequencies. Galvanized pipe can be particularly bad as a ground since corrosion at the threaded joints can cause poor or no connection to the following lengths of pipe. If your house has copper pipe with soldered joints, this is less of a problem. The closer your connection point is to the place where the pipe goes underground, the better ground you will have. #16 or #18 wire size is the minimum that should be used. In fact, 1/4 inch or larger tinned cooper braid if you can find it is even better than wire. Never try to ground to a gas line. If you find you have no good ground available, it is possible to buy ground rods at commercial electrical supply houses that you can drive into the ground close to the location of your equipment to which you can attach your ground wire.

The final connection on the back of your Palomar 90A Amplifier is the power cord. The plug should never be connected to anything but a standard 117 volt 60 cycle AC outlet. The cord and plug are the standard modern three-wire system incorporating a ground wire. If your electrical system does not have the third connection in the wall receptacle, adapter plugs can be found at most electrical stores. A word of caution: Do not depend upon this ground for your system RF ground. Many feet of wire usually exist between most electrical outlets and the actual ground point making it almost useless for an RF ground while being quite satisfactory as an electrical ground.

REAR VIEW TYPICAL INSTALLATION OF THE PALOMAR 90A AMPLIFIER

HOOK UP
Make connections as above. We recommend RG58AU 50 ohm coax between driver or transceiver and the coax connector marked TRANSMITTER on the back of the Palomar 90A Amplifier. The coax should be terminated with a PL259 coax plug at the amplifier end. The antenna should be connected with RG8IJ coax terminated with the same type PL259 coax plug and connected to the coax connector marked

ANTENNA
A #16 or #18 wire, or braid should be connected to the terminal marked GROUND on the back of the amplifier. The shorter the distance to ground and the larger the conductor, the better ground you will have. Connecting all units together with similar wire or braid is also recommended. Lastly, plug the power cord into a convenient outlet, and the hook up is complete.