Adding VFO to Midland 13-898B

[Justin B.]

I have a nice Midland 13-898B and the only thing wrong with it (besides FUBAR clock) is it's 23 channel. I decided it would be nice to have all 40 channels+ so I dug out a DDS VFO I built a few years back for a different project and decided to give it a go.

It was pretty straightforward once I decided which crystal spot to hijack. Here's the quick and easy...

I decided to use X106 - 23.580 MHz - which covers channels 20- 23. I removed the wire to that crystal from the channel selector switch and soldered a .oo1 uf cap to the terminal, attached the center lead of a piece of RG-174 and ran it underneath to the rear of the chassis. Do no ground the shield at the channel selector end, only at the other end to prevent a ground loop.





I didn't want to drill a hole in the chassis so I decided the "REC" jack would probably never be used so removed the wire from it and wired the other end of the coax to that RCA jack.



Plug in the VFO, set channel to 23, and crank in the modified X106 frequency for whatever channel you want. This VFO is controlled with an Arduino Nano so I will probably write some new code to switch between VFO/Freq mode and channel mode. But for now I just made a chart listing what freq to dial in for the desired channels.





Hope this might help somebody out as I got no replies to a thread I started asking how to do it. I would think this should apply to most synthesized radios..

Have fun!

 

[nomadradio]

Our answer to the ground loop problem is to connect a .001uf disc cap from the coax shield to the circuit board ground near the synthesizer circuit. This grounds the braid for the RF circuit, and blocks any DC-ground loop issues.

Very cool! Which DDS did you use? The 985x or the 5351?

73

 

[Justin B.]

I built this several years ago but looking at my notes it's an AD9850. I'm toying with the idea of cutting the front panel to fit a display and removing the FUBAR clock if I can't find another or a replacement motor. So far no luck on that...

Thanks for the cap tip, never thought about it that way just remembered a lot of my boat-anchors use the "ground one end" method... I really wasn't sure if coax would be a good idea due to possible added capacitance but it seems to work OK.

73,

 

[TM86]

I have one of these that the clock and meter were fubar when I got them. The equivalent AM only model clock and meter fit perfectly.

Didn't think about putting a DDS VFO in it, though.

 

[DanD]

I have a nice Midland 13-898B and the only thing wrong with it (besides FUBAR clock) is it's 23 channel. I decided it would be nice to have all 40 channels+ so I dug out a DDS VFO I built a few years back for a different project and decided to give it a go.

It was pretty straightforward once I decided which crystal spot to hijack. Here's the quick and easy...

I decided to use X106 - 23.580 MHz - which covers channels 20- 23. I removed the wire to that crystal from the channel selector switch and soldered a .oo1 uf cap to the terminal, attached the center lead of a piece of RG-174 and ran it underneath to the rear of the chassis. Do no ground the shield at the channel selector end, only at the other end to prevent a ground loop.

View attachment 77020



I didn't want to drill a hole in the chassis so I decided the "REC" jack would probably never be used so removed the wire from it and wired the other end of the coax to that RCA jack.

View attachment 77021

Plug in the VFO, set channel to 23, and crank in the modified X106 frequency for whatever channel you want. This VFO is controlled with an Arduino Nano so I will probably write some new code to switch between VFO/Freq mode and channel mode. But for now I just made a chart listing what freq to dial in for the desired channels.

View attachment 77022

View attachment 77023

Hope this might help somebody out as I got no replies to a thread I started asking how to do it. I would think this should apply to most synthesized radios..

Have fun!

Thank you for the input I have one of these great base radios too and was trying to figure out which way I wanted to go with it so I could use it more

 

[Justin B.]

Here is a VFO freq to channel translation matrix for my particular radio.

 

[SuperLid]

I have a nice Midland 13-898B and the only thing wrong with it (besides FUBAR clock) is it's 23 channel. I decided it would be nice to have all 40 channels+ so I dug out a DDS VFO I built a few years back for a different project and decided to give it a go.

It was pretty straightforward once I decided which crystal spot to hijack. Here's the quick and easy...

I decided to use X106 - 23.580 MHz - which covers channels 20- 23. I removed the wire to that crystal from the channel selector switch and soldered a .oo1 uf cap to the terminal, attached the center lead of a piece of RG-174 and ran it underneath to the rear of the chassis. Do no ground the shield at the channel selector end, only at the other end to prevent a ground loop.

View attachment 77020



I didn't want to drill a hole in the chassis so I decided the "REC" jack would probably never be used so removed the wire from it and wired the other end of the coax to that RCA jack.

View attachment 77021

Plug in the VFO, set channel to 23, and crank in the modified X106 frequency for whatever channel you want. This VFO is controlled with an Arduino Nano so I will probably write some new code to switch between VFO/Freq mode and channel mode. But for now I just made a chart listing what freq to dial in for the desired channels.

View attachment 77022

View attachment 77023

Hope this might help somebody out as I got no replies to a thread I started asking how to do it. I would think this should apply to most synthesized radios..

Have fun!

Love it.....I did the same with a Hy-Gain V 674B this past winter. Similar radio as you probably know. I had that thing set up for at least 2 months straight. It was really nice to use.

I had the 898B with a Siltronix 90 in the 80's. It's a blast!

 

[Justin B.]

Finally finished up this project. I added a SPDT switch to the back of the chassis to switch channel 23 position between VFO and the original crystal. Everything works great and if I can ever find a clock motor this will be a perfect base station.

Here's some final pics:

I removed the .001 uf cap from the channel selector and soldered the coax center lead to the lug and then ran a wire from the crystal to the vicinity of the switch.



Next step was to drill a hole in the rear of the chassis and mound mini toggle switch. The center lead of coax hooks to the common terminal of the switch, The center of the RCA jack hooks to one of the other terminals through the .001 uf capacitor. Finally, the wire routed down from the crystal is attached to the other switch terminal.



Final step was to label the switch on the rear to remove any confusion! The switch positions will be determined by where you soldered the wires on the switch.



Hope this fun little exercise might help somebody in the future and the concept should work with numerous other rigs. I'm getting ready to do a Pace Sidetalk 1000.

73,

 

[nomadradio]

Excellent job!

Pace Sidetalk 1000

Just watch for glitchy connections from top side traces to bottom side foil traces. They used small pins commonly called "griplets" soldered to foil on both sides. They have a tendency to develop fatigue cracks and cause intermittent faults.

73

 

[doffo]

Do you have information on building/parts to the VFO? I considered this to one of my 23 Channel Kraco SSB radios, and you done exactly just that.