I was asked recently by one of the "Inland ARS" members what my 6 meter system would bring to the Inland ARS repeater system. I can tell you that at the instant the question was asked, I was really taken aback! My first thought was, what does he think it will bring, or, what does he think it should bring? I guess I might better re-phrase this last thought to read, "is there some anticipation of what this should bring?"

Let me try and start by giving the reader some over-all views of Auxiliary Link Systems (commonly called "Remote Base Stations"). You see, its not just a repeater! I should also say that I really love writing articles like this, that relate to specific questions I have been asked. This is probably because most folks who ask such questions probably expect some singularly explicit answer. With such a question, no short answer is possible. The planning and construction of a remote radio facility is more art than science, its the concrete embodiment of a conceptual goal. But, back to why this is true!

An Auxiliary Link fulfills the design protocols of its designer. This implies that a purpose is in place to achieve. That is certainly my goal, as it has been with every Ham I have ever known who has built a "machine"! You see that we must look at any conjoined activity between a discreet 2 Meter wavelength repeater, and a separate 6 Meter repeater as a "remote function". Thats where the "remote" or "machine" comes in! Ah, the "machine" here is another telling concept!

In the mid 1960's a number of Ham's in Southern California were building "remotes". As their ideas coalesced to the point where they made these remote radio devices respond to their wishes, and could re-configure them to support any goals or desires of the "user base", that means the guys footing the bill, they came to say, "we sure have a real machine here"! This means, its not just a repeater that sits up there and repeats anything that comes along on the input frequency, this "box" does a bunch of chores! Keep in mind that all such systems were designed and built long before anyone thought of owning a computer, and the micro-processor was still about 10 years away!

So what are the basic differences between a "Remote Base" ( and I'm not talking about some flipping cross band repeater ), and a conventional repeater system? First a repeater uses only two frequencies, an input, and an output. A remote base, or Auxiliary Link System may also use conventional "inputs" and "outputs" but, it also has operating additionally an "uplink", "downlink" and perhaps additional frequencies for telemetry and other control functions. It is in the simplest sense ALWAYS a "full duplex system". This means whatever is happening with any of the downlink transmitters or uplink receivers, the control operator always knows whats happening. He or she has instantaneous feedback and control of whats going on! Now at this point I could go into how this works but, let me get back to that question that was asked of me. If I start answering at this point what I see in the potential of a "remote base", I'll really only be telling you of what I see as the ideal machine. Ah, what the heck, heres what I think is the ideal remote base!

First, it must have frequency flexibility, or at least wavelength flexibility. This implies of course that the system under use can relate well enough to the person who is listening and controlling from some remote site. For this reason, crossing modes is probably a bad idea. So, an FM system should control only similar structured systems that sound and respond similarly. Ok, if thats a basic criterion, what bands can such a "machine" engage?

Certainly 10 Meters, its a great band for FM! But, Ooops, we have to be careful to keep in mind the license class and operating privileges of all who might "bring up" the 10 Meter transmitter. Probably best to keep all the radios within the "Tech Bands". Ok, cool, the next band then is 6 Meters! Wow, thats great! 6 Meters is even a more scientifically interesting band than 10 Meters is, and anyone can operate there! So what could a remote base do that has 6 Meter FM, in addition to other bands?

Well, if we only think in terms of a repeater, that lends one prospect. Certainly all repeaters support sort of a "family" that lives on any given repeater. 6 Meter repeater families are often quite interesting. This is because the nature of the band, and mode, offers a unique propagation situation. Also because the "noise floor" at the 50 MHz. band is greater than any of the higher frequency bands, 6 Meter band operators get used to having radios with excellent noise limiting. What I am saying is, if the radios used by each of the different "user stations" provides at least 50 Watts of output power to help guarantee good receiver quieting at the other end of the transmission path, and has a receiver of decent sensitivity that provides at least 40 dB's of noise limiting, that user has a real intercom. That is not only a local intercom but, one with DX potential.

I used to drive around anywhere in Orange or L.A. county, and have complete full quieting response from the mountain top radio I was using. And in those days, I was using (by todays standards) a pretty flaky radio! I had a Motorola T41GGV in the trunk of my '64 Ford Galaxie. This radio while sporting about 20 vacuum tubes in the receiver, and another dozen and a half in the transmitter, not to mention a mechanical vibrator to provide B+ voltage was still a good radio!

This radio put out 25 Watts of RF, and had about .25uV sensitivity for 20 dB's of receiver quieting. It did have better than 40 dB's of limiting! I could talk anywhere in the basin, and it was nice full quieting very nice fidelity FM! I also often worked at least single hop DX on this same frequency of 52.525 MHz. Of course the mountain top radio was doing quite a bit of the work! Although I would regularly work this DX contact via the repeater, then switch to simplex on this same frequency, and do it again.

I guess I should point out that in those days 52.525 MHz. was used both as a simplex frequency, and as a repeater output. The input frequency was at 52.760 MHz.. Also, most stations monitored their own transmissions by listening to a 440 MHz. frequency that downlinked a mountain top remote receiver on 52.525 MHz.

Now of course a 6 Meter repeater is quite different than a 2 Meter repeater. You see, 2 Meters just about never opens up to places that are 1200, or 2400 miles away. 6 Meters does this fairly often! If the 6 Meter "box" fed some telemetry to the 2 Meter host radio, such as a change of courtesy tone, folks on the 2 Meter "box" as well as the control link would know there was an influx of 6 Meter activity! At this point either a control operator, or in some cases simply a two meter operator might hit a Touch-tone digit, and this would enable the 6 Meter box for a period of time.

Now of course one thing has been not quite left out, but rather skirted over. That is the implication that all users are operating "duplex". Practically no one does this now. This is because Japanese radios don't avail themselves of duplex operation, that is simultaneous receive and transmit, on the same band. All FM Hams of an earlier era did this whenever any sort of an input/output frequency status was involved. Well, if we can't operate single band duplex, why not cross band duplex? When the remote mountaintop radio is enabled, all operators could listen on one band, and talk on the other one.

Now of course a great benefit for the operator is that he or she can operate a "dual diversity" station. By listening to "what the hill hears" on one receiver, and by listening directly on a 2nd. receiver, gives you excellent response to the communications path. In this situation you would say listen to 6 Meters directly in your car, and also be listening to the mountain top 6 Meter receiver as conveyed via 2 Meters.

Other potentials that exist are for basic telemetry. Such things as knowing how good your signal is up on the hill with an "S-meter function". When this function was enabled operators could have direct dBm feedback of what their signal is up on the hill. This function of course provides a means of testing antennas and power amplifiers. This in conjunction with a function that will let the downlink transmitter change effective radiated output by 3 decibels gives a world of information to the technically minded Ham. Its also nice to know the weather up on the hill. Temperature, wind speed, and other similar data can be conveyed via the control "talk-back" frequency. You can even tell if someone entered the repeaters vault building!

Well, it looks as if I have devoted about five pages to that gentleman's question. There are many more things I could say about Remote Base Stations, I have known many Hams who built some of the best of them! I'll leave with this article as it is for the time being though. We'll wait and see what further questions develop. I'm hoping there will be such questions, because the essence of Ham Radio is building and experimenting!

Terminology utilized in this article:

Box: In the context of this article a "box" is considered to be a receiver, a transmitter, or a combined configuration of both. Sort of a "black box" development scheme!

Bring down: A term used to mean to deactivate or disable a particular radio function.

Bring up: To activate or enable a radio function in whole or in part.

Communications Path: This is an engineering or scientific concept that considers where the signal is going or how it gets there. Such radio signal paths might be bounced off various layers of the ionosphere, or even the ionized trails of meteors.

dBm: Decibels above or below 1 milliwatt. The typical radio engineering use would assess signals at various minus dBm levels. A minus 20 dBm (-20) signal is equivalent to 1/10th of a microvolt at 50 Ohms impedance. Or, if I have a -23 dBm signal on the hill, then switch to a 3 dB gain antenna, or otherwise double my power output, the S-meter telemetry from the hill will next indicate that my signal has changed to minus 20 dBm.

Downlink: In the simplest sense you might think of a repeaters output as its downlink. What is really implied though in a true remote base station is not only duplexed audio response but, any additional telemetry that tells the operator of the Auxiliary Links operating status.

Dual Diversity reception: This is a method used by the military for decades to obtain the most information or content and knowledge conveyed along the signal path. This scheme utilizes two or more receivers to listen to all aspects of the signal. This is a great scheme to employ at a repeater site because of the repeaters high elevation. You see the higher the radio is in the air, the lower its angle of radiation on both receive and transmit, and consequently the longer the communications path. With dual diversity the operator can listen to signals at both lower and higher angles.

Full Duplex System: A duplex system is one in which any given station listens to the downlink, as he or she is transmitting on the uplink frequency. In a full duplex system the operator would by some means also listen to the uplink frequency.

Machine: The name given to the first Remote Base Stations built in Southern California. In more recent times Hams commonly call repeaters "machines" but, its not a machine until it does something more than simply repeat!

Remote: An abbreviation for "Remote Base Station" or as the FCC calls them, Auxiliary Link Stations.

A bit of trivia here! Remember in the movie "Star Wars" when Oby Wan Kenobe first tells Luke Skywalker to "use the force" when he is batting at a little baseball size "remote" with his light saber? There are many such FM Ham references in this movie! In fact Han Solo's ship the Millennium Falcon was parked at loading dock "94" (pronounced nine-four). Nine Four, that is 146.94 MHz. was probably the most commonly used remote downlink frequency of the mid 1960's through mid 1970's

Talk-back: This refers to the talk-back or downlink transmitters at a given remote hill top. Keep in mind that often, many such hill tops are linked, and the talk-back of each may contain some subltlely different content and information.

Telemetry: Many forms of telemetry or "tele-metering" are possible. They can exist quite transparently, such as modifying the downlink transmitters hang time. Or, they can be more obvious such as distinctive tones, or even analog to digital signaling. These days it is even common for the mountain top radio speaking with its own voice, and telling operators whats going on.

Touch-tone: Touch-tone is the licensed trade name originated at American Telephone and Telegraphs "Bell Labs". The ATT folks at Ma Bell envisioned people using their telephones for all kinds of remote control applications. Hams however were the first to capitalize on these Dual Tone Multi-frequency (DTMF) signals. Before this they used single frequency tones, and stepper relays.

Uplink: This is the frequency used to "uplink" both voice and commands to the hill. In addition to vocal input, commands and telemetry can go up to the hill on this frequency. Some of these signals stop at the machine, and others are repeated by the machine.

Vault: This is one common term used to describe the building that the machine is housed within.