Midland 42DS TX scale

Hi all,

I bought a Midland 42DS, to try and rekindle a bit of CB. It’s a handy little device, and comes in a good package offered with two battery packs and an external car adapter. After purchasing it I went off to the local electronics store and bought 14AA rechargeable NiMH batteries with 2100MAH each. I charged all the batteries and fired the thing up. However I cannot understand one thing. I connect the 8 pack battery and power on the TX scale indicates around 1,5W of power. Using the exact same battery pack I disconnect the rubber duckie and connect a mag mount, hit the PTT again and the power scale goes up to 2,5W. I then switch to the 6 pack, and with a rubber duckie I squeeze out 0,75W, then move onto the mag mount antenna and there is a TX power of 1,5W. Finally I move on to the car power adapter, and regardless of the antenna I use, it throws out full power according to the TX scale which indicates 4W. In all cases i connect the antennas via the BNC connector on top of the radio. Even though the car adapter has a PL-259 socket it seems that you can work with either antenna attachment point. Is there a way to somehow transmit at 4W using the 8 pack? Or am I on some sort of wrong setting? It’s weird having such a big radio with less than half the power of a Baofeng. Thank you,

73’s

Hi Antonio,

Your power output on that radio, (and typical of others), will depend on the power available, i.e. the batteries, and the efficiency of the antenna, (also of course obviously whether the power setting on the radio is set to high or low).

You say that you're using NiMH, which have a voltage of 1.2 volt per cell. As far as I'm aware the 6 pack battery was for alkaline battery use, (6 x 1.5 volt = 9 volt), and the 8 pack battery for rechargeables, (8 x 1.2 volt = 9.6 volt).
If you're using the same NiMH in the 6 pack you'll only have 6 x 1.2 volt = 7.2 volt. So I'm not surprised you're seeing a power output difference.

The antenna will appear confusing as the inefficiency of the rubber duck antenna will seem less so when you run from the cars battery as more power is available. 

I'll have a look out for a schematic and see if you can run from a portable 12 volt battery pack but it'll be a lot more cumbersome.

Anyway, hope that helps.

All the best,
Victor

Hi Victor,

Thank you so much for your reply. In the meantime I ran an experiment using a car jump start pack with a cigarette lighter and it’s exactly as you said. So power-wise I guess the question is settled. With regards to the antenna, then it’s like the radio regulates its power to adjust to the antenna?

Regards,
Antonio

Hi Antonio,

Glad you figured it with the help and your own experiment. It's all good to be learning

There is no power output switching depending on antenna connection according to the schematic.
This radio has a simple single transistor PA, (Power Amplifier), stage so output will depend on the power, (voltage and current), available to it and the efficiency of the load or antenna. The supplied 'rubber duck' antenna is quite inefficient so more power, (again battery current and voltage), is required to drive it. Hence why you saw the differences between antennas.

Hope that helps.

All the best,
Victor

Thank you so much Victor, your help was more than useful.

Antonio

Hi Antonio 
I'm interested to know how you are getting on with the Midland radio? Reason is that I have just picked one up from a friend. My idea is to use it stand alone whilst out riding my push bike, (I'm trying to get more exercise) and ride to higher ground and try it out. 

Victor, I'd be interested to know more about the power pack for this radio you mention if you have the information available? Also any antenna recommendations please? The one I've seen is about twice as long as the supplied rubber duck but they're asking £23 for it at Knights and was wondering if it is worth it?
Cheers guys
Dale 
CT3550

Hi Dale,

I mentioned the supplied battery pack cases for x6 or x8 battery operation, (I also believe you can run the x8 pack with 1.5v alkaline batteries to give you 12 volt), which came with the radio.

Midland Europe link: Midland 42DS specs

If you also have the supplied 'car kit' you can run it from almost any 12 volt source. The car kit will also give you a standard SO239 connection so you can plug into any antenna you desire. If you don't have the car kit then a BNC to SO239 adapter will suit but you'll have to figure out how to hook up another power source.

The supplied rubber duck antenna isn't all that great, (how many actually are?), and you'd be lucky to get much range, maybe a mile or so open air and as little as a 1/4 mile in built up areas. Other antennas are available as you mention or you could even construct your own antenna?

I've never run a CB radio from a bicycle, (there does appear to be some people who have done so on Youtube so might be worth a search), but I have run from a motorcycle back in the day. Let's just say it was fun but a bit disappointing running mobile on the bike....But, I did get some success lugging along a spare motorcycle battery to the top of a hill with a 1/4 wave mobile antenna strapped to some old metal tape measure for a 'deployed' groundplane!

We didn't have PMR446 back in the day but I believe some people have had quite good luck running modern walkies for PMR DX.

Anyway, keep us updated with your bicycle radio quest, it's all interesting stuff!


All the best,
Victor

Hi Victor 
Thanks for the reply. Yes, I'm studying the YouTube videos. So I'm thinking of something like a 3ft Firestik bolted to the rear carrier (metal) and hopefully using that and the bike frame as the ground plane. I've got the cig lighter/so239 adapter so just need a suitable battery, I'm thinking one of those li-on types but not sure which to get for say 3 hours performance? Any ideas? Plenty of high ground around here so should be fun if I can get it to work. 
Cheers 
73's 
Dale 
Cheers

Hiya Dale,

Bicycle frames as ground...and why not? If a biscuit tin does the job a frame certainly will
I can see the Firestik on the rear carrier in my mind's eye, makes me flipping smile!

Got to admit, I'm not up to all that on the battery front nowadays. Don't like the Lithium technology, special charging, cell balancing, blah, blah, too flipping complicated for my liking. Give me a good old lead acid anyday, charge it with anything you have

Be worth asking about batteries on the forum as I'm pretty sure a lot have played around with Lithium tech. 

Anyway mate, keep us updated on the Charlie Tangos, sounds like there some good fun to have!


All the best,
Victor

Yes will do mate cheers 
73's 
Dale

The antenna replacement for the standard rubberduck is called an Albrecht Hyflex. They are 54cm long and work endlessly better than the standard one.

Cheers Firetrap, I'll have a look. 
73's