Hello All,

Some time ago, a subscriber to this list wanted to know how to install a CB antenna on his coach. As promised here are my findings and comments.

Doug Stracener suggested a through-the-glass cellular look-a-like antenna and I suggested using the existing antenna using an antenna splitter made by the Antenna Specialists Co. Although both are a compromise antennas and exhibit somewhat reduced transmission and reception areas, they are an ideal solution for RV use and avoiding drilling holes in the skin of your unit.

Insofar as RV's go, one of the main positive features of these devices is that they keep the antenna profile as low as possible on the coach, hence reducing "antenna strike" damage in the short and long term to both the antenna and the coach

The antenna Doug suggested is common and folks I have spoken with are pleased with the results. If I am not mistaken, they are available from Radio Shack.

The antenna splitter I mentioned is a passive electronic device (no voltage required) that permits the broadcast radio and the CB to share the same antenna. This is a good device for those don't want any more antennas on their vehicles.

I have installed many of these couplers in motor vehicles: Caprice, Crown Vic, Expeditions just to name a few. They have worked quite well according to their users and my observation. PLEASE NOTE: This coupler is not suitable for use with vehicles that have power antennas.

Antenna Specialists ( a division of The Allen Group www.allentele.com ) does not sell these direct, only through their distributor network. The model number for this unit is ASCR-133. Quality CB shops should have them, although I have not seen them in Pilot or the Flying-J.

Another company that has a similar splitter made by CTI is an outfit called Gall's Inc. (www.gallsinc.com) . This company deals in public safety accessories, sells to the public and takes all of the plastic. I bought from them once and was pleased with their service. The part number for their CB splitter is D-APO55 and sold for $26.99 in their last catalog. (NOTE: If you are interested, they also sell a splitter for use with a scanner and broadcast radio antenna that has a BNC connector, sells for $19.99 and it's model number is D-APO93).

On this past Monday, I conducted a test of the splitter. My aim was to install it on our 1997 Safari.

The broadcast antenna on the Safari is located on the road side of the coach. The antenna is a 3-section telescoping mast that extends to approximately 51.5", well within the manufacturers requirements.

The base of the antenna is attached to a point approximately 62" above ground. The first antenna section (each section is approximately 17" long) is roughly .75" from the sheet metal of the coach which bends away until the uppermost section of the mast is the only portion of the antenna unobstructed by the coach.

After extending the mast, I went inside and removed the stereo entertainment center which is located in the cabinets above the gaucho. (I found a minor wiring snafu which I will discuss in a separate post.). I attached the splitter to the coach antenna, then to the stereo and finally the CB ( a Cobra 148 GTL ).

Initially, I tried tuning according to the manufacturers instructions which were to tune "for maximum noise" on Channel 20. This worked somewhat but I was not satisfied with the indicated received signal levels so I had to use my Bird Electronics Model 43 Wattmeter to make a more accurate assesment. The wattmeter showed a high VSWR (standing wave ratio), which I was able to reduce some with tuning but not anywhere near an acceptable condition. ( Not only does SWR affect transmitter performance, but receiver performance as well.). I switched between the "Short Cable" and "Long Cable" ports on the coupler to no avail.

The obvious conclusion is that the coupler will not work in this application. This is due to the close proximity of the antenna to the coach and the severe de-tuning effect this has on the impedance of the antenna. I believe the coupler can be modified to enable it bring the antenna into range, but this is not within the scope of this research at this time although I may try to determine if it is possible at a later date. If it can be modified I will bring this to your attention.

If anyone has questions regarding this, please feel free to contact me either here on the net, or at my e-mail.

Regards,

Jerry