I emailed SCS this question and got back (a somewhat snippy) reply. Posted for those interested.

> I was also wondering if any of your modems can operate in a "TNC" mode
> independant of a computer.

SCS: What is "TNC-mode"?

> I would like to implement APRS tracking, on HF and VHF (300 and 1200
> bd), without the need of a computer full time.
>
> Can your modems do this (with any option or configuration)?

SCS: No, only with a help of a computer, hams do it with a program called UIview.
I never did APRS (I'm always happy if nobody knows where I am) but it seems
to work with this program.

Hello,

I was wondering if the any of the SCS-PTC modems (whatever model/configuration) can operate in your standard TNC mode for APRS operation.

I am looking to fill out my maritime mobile setup with APRS as well as other modes.

I am looking at the PACTOR modems for use with digital modes (PACTOR, WEFAX, email) while I am "online" (computer on/connected). But I am also looking for HF/VHF APRS tracking "offline" (no computer on/connected).

Basically, with a PACTOR modem, XCVR, GPS powered up, I want to track without the aid of a computer on HF or VHF. Is this possible?

I understand if I had a 1200/300baud VHF/HF TNC, that would get me what I want, but it would be nice to have it all in one package. Thus my question about the SCS Pactor modems.

I browsed the manuals, they suggest they have TNC-2 like commands, but nothing that suggests a TNC-2 compatible "mode". Unless I missed something of course.

thanks!
rob

I run APRS on my bike. Here is how I have things setup:

- TH-D7A under the fairing in one of the rear quarter panels. I have the canvas protective cover for the radio to help protect it from moisture and dirt.
- Garmin GPS-135 (surface mount GPS, no user interface) velcroed underneath the lid of my topcase mounted on the rear of the bike.

I do operate the D7A both for APRS and bike-to-bike comms (my wife is licensed and she runs a D7A on her motorcycle).

In a previous variation on this setup, I ran a GPS III velcroed to the top of my tankbag with the interface cable running under the fairing back to the D7A. This worked well but I needed to attach the tankbag whenever I wanted to track.

I have tried various combinations of TinyTrak, HTs and GPS on motorcycle before and determined the current setup was easiest with the lowest maintenance (having to deal with wires, radios, etc).

My bike is a BMW R1150RT

-Robert

Greetings,

I will be putting up my first HF antenna in the coming months.
I have the space for a dipole up in the attic, and I have an existing guyed 20 foot mast on the peak of the roof (currently has a 2m beam). My house is on a corner lot with power lines running on TWO sides of the lot. One of the lines is fairly HV. You can hear noise from the lines on a cold winter day.

Question: Which type of antenna would be best considering possible interference from the power lines?

more data: I have a SW radio (Ten-Tec RX320) which is rated fairly high for "pulling in" stations, but, I have not experienced that great of performance. Currently it is connected to a 100 ft copper wire strung in the attic for the length of the house. It doesnt seem to improve much over the telescoping whip antenna provided with the radio. I suspect because the antenna is paralell to one of the power lines and fairly close to the height of the line that I am not getting much reception. In fact, I get quite a bit of noise. Even after turning off noise generating appliances (computers, flourescent lights, monitors, etc).

Any suggestions?

Robert
KD7DPU

Greetings all,

I have been working on a 2meter setup for my motorcycle. It is sort of a hack of a few different items. Basically I have an off-the-shelf motorcycle intercom system (Autocom EUROcom) which is essentially an "audio mixer" with some automute function. This intercom system has a XCVR connection that will key a radio. I have it connected to a Kenwood D7A.

Everything works fine except that the audio is overmodulated.

Now the headsets in the helmets are homebrew with the mic being your average radio shack condenser microphone. It is powered by 5v with a 33k resitor and a 10 mf capacitor setup (as its packaging illustrates).

Now the questions:

I know it is being overmodulated, but I cannot tell if it is on the input to the intercom, or on the input to the radio. I dont have a way to test this.

Q: How can I reduce the modulation input to the intercom? to the radio?

I suspect reducing the value of the cap at the microphone might help. Is this correct? Are there other ways?

Note the mic is in a fullface helmet, so varying the range between ones mouth and the mic is out of the question (I actually want it close to help keep out wind noise).

I am fairly knowledgeable about beginning electronics, but audio circuits are kind of foreign to me.

Thanks!

Robert
KD7DPU

Greetings all!

I am installing a rig on my motorcycle, which does not have a good ground plane (naturally).

Members of this forum (and elsewhere) have indicated that a 1/2 wave antenna would be better than a 5/8 wave when there is a poor ground plane.

Yet, the counter person at HRO last weekend indicated otherwise (he said 5/8 is better than 1/2).

Can someone definitively tell me which would be better? And more importantly WHY? I am a fairly technical person but new to RF and antennas.

73
Robert
KD7DPU
Anacortes, WA

Greetings all,

I have noticed that when transmitting mobile, something, either the radio, or the RF from the radio, falses the radar detector. Not as a strong threat, just a small "beep". I use the Valentine One radar detector, supposedly one of the best in rejecting false signals.

The antenna is mounted on the roof of the truck cab. The detector is on a suction cup mount on the windshield near the top (near the roof).

What is likely the cause? The proximity to the roof where the antenna is?

The coax for the antenna is what ever is standard for analog cell phones (I am using the old previously installed cell phone antenna base).

Might choking out the power lead to the detector help?

Any suggestions are appreciated?

Thanks!
Robert
KD7DPU

Greetings!

I have a 900 Mhz voice transmitter/reciever. it is fixed on one frequency (not spread spectrum). I am wondering if this can be easily converted to an FRS frequency. Legalities aside, how hard would it be to do this? I dont have a schematic, but I think I can local the crystals. Might it be simply changing out crystals? This thing was made in 1995 and is FM powered by 9 volts.

>>In this set-up it is essential that you use an "random wire" tuner and skip the coax connection between tuner and backstay, - and move the tuner out to the back of the boat and connect the hot end directly to the backstay. <<

Even if I were to use the coax as "one" piece by shorting both ends (see my original post) Seems to me it would electrically appear as "one wire" and simply become part of the random wire.

How about if I just used the center conductor and not the outer jacket of the coax at all???

Referring to my previous post. Running the feedline up the back of the adjustable split backstay is pretty much impossible. The act of adjusting the backstay would foul the feedline. Unless someone has a better idea?

>>Is your backstay insulated at both ends? <<
Yes it is. However the rig is an adjustable split backstay (joining with the main insulated about 8 feet off the deck). This is a 28' sailboat and running the feed up the back (I determined) would cause problems when asdjusting backstay tension. Up inside the mast and down from the top was the only other practical solution I could determine.

>>Regarding ground we have always gone to the keel bolts and toe rails,etc. for a RF ground. <<

Unfortunately we have no keel bolts. It is a fiberglass molded shoal keel filled with lead (large shot with epoxy resin). I have no easy access to the ferrous material contained therein.

>>That little "dyna-plate" may be fine in salt water but I question it's design.<<

The only thing I know about it is that the plate is made of tiny scintered (bronze?) balls packed together that allows the seawater to "seep into" the plate. The packed nature of the "balls" greatly increases the surface area of the conductor exposed to seawater compared to a solid plate of the same size. It is my understanding that the greater exposure to seawater the better for grounding.

>> The 2/10's of a db you loose with RG8X is nothing to worry about. <<

Thanks! This point was one of my prime concerns.

Greetings!

I am fairly new to HF and HF equipment. Over the next few months I will be installing HF radio equipment on my sailboat. I have a few questions regarding proper random wire antenna setup. First a couple of things:

1. I plan on an ICOM 706 with matching tuner
2. The backstay, wire-rope rigging, is insulated (about 30 feet is insulated).
3. I already installed coax leading from the cabin, up inside the mast (about 35 feet high), out the top, and attached to the insulated portion of the backstay.
4. A ground plate has been installed (DynaPlate) under the hull.

Now the questions:
A. The coax is RG-8X (normally recommended for short length VHF-UHF feeds). I was limited by space inside the mast and could not use anything else larger. Will this be a problem? How much performance degradation will I experience?
B. Regarding the ground plane, I expect connecting the outer jacket of the antenna feed (from the tuner) to the dynaplate is sufficient. Is this correct?
C. How "beefy" should the cable to the ground plate be? Will standard thick gauge plastic insulated wire be sufficient? or should it be coax?
D. If the ground side of the antenna is not going up the mast, then the outer jacket of the coax up the mast would not be used. Would it help to short the center wire and jacket of the coax on both ends and connect this to the back stay for the "active" side of the antenna? Seems to me this would make a larger "pipe" for the signal and help compensate for the smaller RG-8X coax center conductor.

Additional:
I plan no more than 200 watts into this rig.
I am not looking for absolute "optimal" performance, just the best I can reasonably get considering my mast situation (pulling off the mast to install larger wire is NOT an option).

I would appreciate any insight others can offer.

Thanks!
Robert Sutton
KD7DPU
Anacortes, WA