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Troubleshooting a Preston MDR1


Danger Charles
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Hey all-

I'm trying to keep my old Preston MDR1 alive and am in the process of replacing a few cables and accessories, but in the process have come up with a few questions/curiosities.

The first thing I was trying to sort is the command port antennas.  The system technically works without them, but is very unreliable, with the motor stuttering.  On the hand unit side, it's just a straight bnc out, but on the MDR side I have a command port to bnc adapter which is barely holding together.  Also, the lemo pins of the antenna have all been deliberately snipped except for one...  That all said, should any generic BNC antenna work as a replacement for the hand unit?  On the MDR side does anyone happen to know what the deal is with snipping the pins?  Was this some common aftermarket mod?  Any idea how I might replace this part?  Thanks!

 

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>>  should any generic BNC antenna work as a replacement for the hand unit? 

Well, you're probably going to have to have _some_ idea of what frequency you're dealing with. Getting this exactly right is less important on the receiver than the transmitter, but you want to be in the right ballpark.

I don't have anything here in front of me but there might be something in the documentation or look for a sticker on the transmitter unit, often there's a FCC mandated label. 

Assuming you're in the US, go to the DigiKey website, RF/IF antennas page

     https://www.digikey.com/en/products/filter/rf-antennas/875?

Narrow the search by putting in your frequency band in the "frequency center band" column (6th over) and check 'BNC' and 'BNC male' in the "termination" column (15th over)

There are about 60 hits for little BNC stub antennas in a variety of frequencies, so if it's just the missing antenna, it's likely you'll be able to find a reasonable replacement there.

>> On the MDR side does anyone happen to know what the deal is with snipping the pins?  

It was probably just a matter of limited space, and the antenna was only using one pin... so....

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Thanks Steve!

Per the manual (which is archived on Preston's website and clipped here) it looks like 2.4 GHz is the frequency, and digikey/amazon has a few good options it looks like.

Also, if it happens to help anyone else, I called Preston and one of their engineers was happy enough to send me over a wiring diagram for the command cable FWIW:

 

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Preson MDR1 Command.png

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