Part15

License Free, legal, low-power radio broadcasting

Palomar 1750 Meter Transmitter

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Looking through my low power equipment file folder I came across a news item from the early 90s clipped from an electronics magazine announcing the 1750-meter transmitter kit from Palomar Engineers (160 to 190 kHz) intended for Part 15 long wave. $145.00

The company exists today but there is no mention of the transmitter. I have e-mailed them to ask for a history.

http://www.palomar-engineers.com/index.html

If they respond I will post the information here.

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Comments

  1. Capability
    Key question would be does this unit have the capability of various modulation methods, or is it a mere CW unit only, or SSB unit only.

    Keep in mind that 99 percent of the consumer radios on the wally world shelf and rat shack shelf receive the LW band in AM mode. It is only the specialty radios such as that used by hams and DX enthusiasts that have those 500 dollar and up radios that can receive these other modulation methods.

    I seriously doubt that the average consumer is going to fork down 500 bucks for a radio capable of LW reception, and then go through the tuning steps to properly tune in a SSB transmission or even a CW transmission.

    If this is for the LW network project, I recommend to everyone who will be setting up a LW station to have a transmitter that operates with modulation scheme that the majority of available radios can receive and demodulate. And that would be A3E…AM.

    Unless this LW network is going to be nothing more than a nationwide cluster of CW signals or wish wash swahh swahh SSB signals..it will not get anywhere at all with the general public.

    RFB

    • Important Point
      You raise an important point, RFB. For my part also I am only envisioning an AM modulation-method long wave transmitter, and here is what the description says about that:

      “Palomar Engineers designed the transmitter for CW operation, but reports that it can easily be amplitude-modulated. Operating frequency is determined by a plug-in quartz crystal (not supplied).”

      So far it appears that the transmitter is long out of production, but my e-mail to Palomar got returned because I forgot the dash in the address, so I have sent it again.

      Right now, for the long wave network project, there is an emerging circuit being developed called “Deep Voice,” and the transmitter being designed by RFBurns.

      North Country Radio’s transmitter, by the way, does list 1-watt capability, a question recently asked.

      • Original Concepts
        “Right now, for the long wave network project, there is an emerging circuit being developed called “Deep Voice,” and the transmitter being designed by RFBurns.”

        I think I will start a new Part 15 LW transmitter kit company and call it “Original Concepts”.

        Actually my unit on the test bench is still embedded into the prototyping board. I am debating on adding a microprocessor and direct digital synthesis to generate the carrier, far better than a PLL design.

        Earlier I stated that the unit will have multiple modulation modes, but I do not see the point in that when the goal here is to revive the LW band and reintroduce it to the general public who is not going to spend no more than 2 seconds tuning in a LW frequency and expecting to hear something they recognize right away.

        And as I pointed out, the radio they are most likely to use will be one that only demodulates in A3E mode anyway. It would be a waste of time and resources to construct a unit with multiple modulation modes when in the long run..the only one that will matter is AM.

        RFB

        • Simple LOWFER Transmitter
          Here is a LINK TO A SIMPLE LOWFER TRANSMITTER that would be inexpensive fun.

          Although it’s designed for use as a beacon, it could probably be modulated such as was the PIXIE transmitter. I don’t know much about modulating a CLASS E output stage but I suppose high level modulation would work. Any input on that?

          Anyway, low parts count of easily obtainable stuff and the layout at that frequency should not be a problem to make it work.

          • i have a stack of lowdown
            i have a stack of lowdown magazines from lwca. in one of them is the schematic for the palomar. in few weeks when my arm is better i will dig it out and scan it.

          • Modulating Beacon
            “I don’t know much about modulating a CLASS E output stage but I suppose high level modulation would work. Any input on that?”

            The final in that “LOWFER” beacon is very similar to the final used in the TH series transmitters, with the exception of a couple of components, but is basically the same. The TH units use high level modulation through a current amplifier circuit tied to the B+ rail feeding the output pair.

            Do not see any reason why the LOWFER beacon’s final can’t be modulated in the same manner.

            RFB

          • anytime you are limited by
            anytime you are limited by input to the final it makes sense you want as much efficiency as possible out of that final and antenna/coil system.

          • The LOWFER Circuit
            Thank you MRAM for posting the LOWFER circuit and article, which I have been enjoying as a mid-morning read.

            In case Neil Radio8Z glances this way, is this oscillator one that might work with the DEEP VOICE long wave re-build of Big Talker?

            ALSO, looking ahead to the antenna stage, I doubt that most stations will erect a 50-foot vertical, so what more buildable choices would be good? How about Inverted Vee?”

          • Alternatives
            Why not try the slinky. Or a pvc pipe 25 feet long wrapped with 50 feet of wire.

            Or an Isotron.

            Or slanted 50 foot wire.

            Or the inverted v.

            As to the oscillator of the lowfer to your big talker, yes it would work..why wouldn’t it?

            RFB

          • Truth in Lending
            That’s an old banking term, “truth in lending,” which apparently never happened, but here is the truth about why I wasn’t sure…

            My experience in design electronics is only recently rekindled after a long break from audio video recording, which is different from RF, and mainly schooled back in the tube days. So I don’t want to act too confident about what will work when it comes to mixing and matching transistor/IC circuits. I wonder, “Will it have enough gain”,”Will the impedances be right.”

            I like all those antenna choices. The slinky is still in its box.

          • Wonders Of The Radio World
            “I wonder, “Will it have enough gain”,”Will the impedances be right.”

            This is where a buffer stage comes in. Placed between the oscillator stage and the final, it can provide the impedance matching and it can also be set up to provide a touch of gain if needed to provide enough drive for the final.

            The slinky approach for a LW antenna is probably the best quick approach for it. Since it is merely a coil that can extend and retract, all one needs is to calculate how many turns is needed in the overall slinky and then simply extend to the appropriate length in relation to the coil turns. And just like a 3 meter stick, its feed point should be close to the ground so that your ground lead is short as possible to the ground system.

            It will work…and work quite effectively to boot. Put the finished slinky into a pvc pipe and secure with expansion foam as suggested by another member to keep the slinky in place inside the pvc pipe.

            However my choice would be to put the slinky on the outside of the pvc pipe and then coat it with varnish. That way any atmosphere corrosion or build up of elements won’t affect the performance by coating the outside of the pvc pipe with attenuating minerals etc. The varnish will prevent the build up and protect the slinky from oxidation. Plus you will be able to keep the winding separations uniform throughout the entire length of the slinky before securing it with the varnish coatings.

            RFB

          • I’m Glad You Guys Are Working On This
            Palomar had a really good receive
            converter that took 10 kHz to 500 kHz
            and boosted it up to the HF range. That way
            you could tune VLF in on an HF communications
            receiver.

            The one I used was loaned to me from a
            friend.

            This isn’t quite what you guys are talking about
            but the info here brought it to mind.

            Best Wishes,
            Bruce, DOGRADIO STUDIO 2

          • No Word
            Palomar has a website which lists very few products in the toroid and connector line, but has not responded to my e-mail about the transmitter.

          • Question re: TX Oscillator
            In response to Carl’s question “In case Neil Radio8Z glances this way, is this oscillator one that might work with the DEEP VOICE long wave re-build of Big Talker?”

            Yes, it should. The 74HC and 74HCT series of ICs provide fairly robust current drive capabilities and can drive the base of a low power final amplifier adequately.

            In my “High Efficiency” AM tx. I used a digital gate for the oscillator and driver as shown here: http://postimage.org/image/u4s399f4t/

            This is only to illustrate how the coupling works and for the Deep Voice the coupling cap C12 and resistor R15 may need to be changed due to the lower frequency. Using a counter to divide down the crystal frequency helps because it permits use of higher frequency crystals which may be easier to obtain.

            One comment on the transmitter schematic MRAM1500 linked is that the push pull output may kill the efficiency if both final transistors are conducting at the same time. If the drive signal is a square wave with fast rise and fall time this may not be an issue. Note the use of base to emitter diodes to keep the coupling capacitors charge under control.

            Neil

          • Not A Linear Output…
            Would that output stage be considered as a traditional “push pull” or a “totem pole” output not unlike TTL logic chips use?

            In a traditional push pull both transistors would source current to the load but in the totem pole only one transistor sources current while the other only sinks current.

            The drive from the logic chip would be square, fast rise/fall time. The author refers to this as adding to the efficiency. I suppose this would be a Class E output.