Hi folks.
We have a hamilton rangemaster that we use at a school for parents waiting in the parking lot.
I sent it back in to be serviced and somewhere between the company and my office the crystal was removed and is now missing. I wrote to Keith and he explained that he cant get the crystals anymore and wanted 100 dollars or so for an agile one. In the education world, thats a LOT of money. Do I have any other options?
The first thing I would do is to try to find out what happened to the crystal and either get it back or get reimbursed. Was the shipment insured? Why would anyone steal a crystal? Talk to the carrier.
Unfortunately, crystals cut to a specific frequency, especially for the broadcast band, are getting very hard to find. You might try contacting ICM, a crystal manufacturer, but the cost might be high.
Another option is to build your own PLL circuit such as this one:
http://www.tompolk.com/radios/frequencysynthesizer/freqsynth.html
Otherwise, getting the synthesizer from Hamilton might be the most practical way to get back on the air.
Neil
Thanks Neil.
The repair was made a long time ago, and its been moved around a lot so I don't think it was during shipping but after it arrived. We are just now getting around to putting it up.
Keith is looking for one and I have found a few on the web. Thanks for the circuit-- it looks ideal but powering it off of the Rangemaster power supply concerns me. How would i get power to the circuit?
There is a caveat if you use the PLL circuit. The 4046 IC specified by the author is not one which I would choose because the typical maximum frequency specified on the data sheet is too low. I have built similar circuits but used the 74HC series of integrated circuit chips and all of those I built work fine. Another forum member is currently posting about problems he is having using the CD4046 chip.
The circuit of the Rangemaster is unknown to me so the best I can suggest is to use a small regulator such as the 78L05 to supply the 5 volts needed for the synthesizer and get the power and ground from the DC feed line to the Rangemaster. It is possible that a 5V supply is available on the Rangemaster board but I would hesitate to try to tap into it unless I knew more about it.
Unless you are willing and equipped to build and test the synthesizer you might be best advised to find a crystal or buy the synthesizer which Keith offers.
Neil
In frequent posts during recent months I've noticed mention of the scarcity of crystals cut to medium wave frequencies.
One gets the impression that MW crystals were common at one time but are now "discontinued."
When and why did MW crystals fade from the scene?