Yes.
But it’s a different use case Colin. I did think of acquiring an MTR but the current price is a bit steep for what it is IMHO. But I have far too many pieces of gear that don’t get used that I need to reduce not increase the number of radios.
Very true. I guess it will depend on the intended usage but in my case it seems to fit the bill.
Same situation for me, Andy. 
But the conversion to 60m and in particular the free space inside the MTR4B is a great challenge to fill up with something special,
e.g. a next generation battery, paddle, speaker, wireless phones & paddle & station control, …
I think they are quite reasonably priced for what they are. They must be made in very small production runs and they are far from an easy build having a double sided smd board and lots of components that can only be hand assembled. I suspect that only one smd side can be done with a pick and place machine. It is unrealistic to compare them with a mass produced, mass market, radio like an FT817.
We’ll have to disagree then. I wouldn’t pay £310 for what you get. It’s not that it’s not a good radio or the people involved are profiteering. No, but it’s over half the price on an 817. And don’t forget, with an 817 you get significantly more weight and volume to the radio. And weight (and current draw) is something that is very sadly lacking on these trails radios.
Maybe; maybe not. My point was merely that comparing the size and weight of a rig designed to give you that capability/flexibility with a rig designed for a much more limited flexibility isn’t valid. They’re both good radios in their own way (with compromises as always)
I think the comparison is valid in this case.
It seems as though our friend Arnaud uses his FT817 for HF CW, therefore swapping to an MTR will save a lot of weight.
Of course I’m not saying that an MTR is equivalent to an FT817! An FT817 is very much a multi purpose rig, it does lots of stuff quite well. An MTR is extremely specialised an does trail friendly CW extremely well.
I love my FT817 BTW, it’s great for taking on holiday when you don’t particularly know which mode or band you fancy beforehand. I took my FT817 to Mull in September, I had great fun operating from the holiday cottage.
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Thanks Peter, your MTR 60/20m looks really nice!
Along G8TMV “I will need then a toolchain (which is free) and a programmer (the launchpad is about $10)”.
I’ve never updated a program this way, so suggestions for suitable tools are welcome.
There’s various resources on the AT Sprint Yahoo group if you’re a member.
Flashing the firmware isn’t too bad, I think there’s just three wires to connect to the Launchpad.
I had to reflash the MTR-5B a few times due to bugs in the initial releases.
I’m sure someone would be able to help out with the firmware changes, assuming that the 4B firmware is available.
Thanks Colin!
Since there is no separate folder under “Files”, I have to look around a bit.
Silly question: The MTR-5B states a voltage of 9v-12v. What is the tolerance on this? Usually my full battery starts at around 13.4V, would I be frying the MTR-5B with that?
Thanks
The MTR PA transistors tend to blow up at voltages over 12 Volts.
ok, thanks.
The problem comes from the fact that the PA transistors are TO92 package BS170. There’s 3 transistors in parallel.
5 watts from three tiny transistors without heatsink is quite impressive don’t you think?
More power out = more reflected power in a bad load. It’s the bad load case that causes the issue.
An MTR will happily survive TX into an open, it’s reactive loads which will cause the PA to fail.
Don’t for one minute think that the MTR PA is not up to the job, because it is, providing you treat it with respect.
The PA is optimised for operation from 9v, increasing the supply voltage will increase the RF power out but with diminishing returns towards the top end of the range.
A number of users have used 3S LiPo battery packs with their MTR and the rig seems to work fine. A fully charged 3S tops out at around 12.65v.
73, Colin
Thanks for the info. Actually I think I read somewhere that the MTR puts out 2.5w vs the 5w of the 817. The downside of the MTR is that I would have to buy yet again new batteries but it would be for a smaller weight on the other hand. 2.5w is a bit tough going these days (I know some ppl have amazing QSOs with 100 mW) 5w would have been nice, but nothing’s perfect.
Look at my chart above - MTR puts out in region of 5W from 12V supply. The PA is directly connected to the supply, so increasing the voltage increases the power output.
Nothing lost in terms of power output over FT817. The MTR is so efficient that you can use a really tiny battery - even a 9v block battery (PP3/MN1604) if you’re really stuck. A small 3S LiPo with a few hundred mAh capacity would power a few activations at around 4W output. My 3S battery cost around £7 GBP.
I sometimes run a 2S battery which gives me about 2w with the MTR.
I wouldn’t be put off by a lack of suitable power source, as the cost of obtaining one will be minimal.
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It makes sense, thanks for the explanation.
In a different tx kit I get way less than 2.5W with these PAs.
I must be doing something wrong. (I have heatsink etc)
It depends on how they are set up.
In the AT Sprint series of radios (including MTR) the FETs are driven with a square wave and are biased for class E. The PA low pass filter is actually an important part of the PA, not just there to clean up the signal.
Because of the efficiency, very little energy is wasted as heat and therefore no heatsink is required.
A similar kind of PA is the NS-40 (None Simpler 40), these kits are available via Ebay from time to time. Four State QRP Group
I have just received an MTR4B and would like to share my first impressions and benchtest results. My subjective point of view may be biased a bit due to the successful use of the MTR3B Mountain Toppers in 60 SOTA activations with a total of 3385 QSO.
Subjective point of view
The MTR4B looks all around very clean processed. Dimensions and weight are, as expected, significantly greater than those of the MTR3B.
The front panel with the very well readable display looks fantastic and conveys a touch of luxury. Nothing to complain about the user interface in connection with the display, almost perfectly solved.
The bottom of the case looks virtually indestructible, but this makes it quite heavy.
Overall subjective impression: A masterpiece of technical design - made to love and enjoy it!
Benchtests performed
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Accuracy of voltage display: ok (0.1V@6V … 0.2V@12V below supply voltage)
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RX current 30mA@6V (no antenna): ok (31.87mA)
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(RX current @6V (no antenna): 23.42mA)
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RX current 20mA@12V (no antenna): ok (18.87mA)
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Supply voltage range 6-12V in RX and TX mode: ok
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Band annunciator: why “9” and not “8” for 80m? (other bands ok)
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Power output at supply voltages of 6/9/12V
20m: 1.09/2.17/4.32W
30m: 1.41/3.24/5.76W
40m: 1.41/3.14/5.57W
80m: 1.90/4.28/5.76W
- Power output 2.5W +/- 250mW@9V: not fulfilled (see above)
- Power output 3-4W@12V and up to 4.5W@12V: not fulfilled (see above)
- Accuracy of op frequency: ok/30-50Hz too low (Reference PFM1300, K3/P3)
- TX signal quality: ok (Reference K3/P3)
- TX/RX Transceive accuracy: ok (Reference K3/P3)
- Sending speed of stored messages: ok (was/is not “perfect” on the MTR3B)
- Direct frequency entry: ok
Technical point of view
My MTR4B fulfills - with the exception of the power output (see above) - its specification/product summary in all tested cases.
From my point of view it is absolutely incomprehensible that the power output is not best matched to the same level on all bands before delivery. BTW, the same applies also for the MTR3B.
Such things unfortunately reduce a specification to an empty marketing phrase.
Another questionable point is the high power output of significantly more than 5W at the maximum permitted operating voltage. This will almost certainly lead to problems under operating conditions with a not perfectly matched portable antenna - also a freshly charged 3S accu will increase this risk even more.
Overall technical impression: The MTR4B is undouptedly a technically high-quality product based on its field-proven MTR predecessors. So it is highly regrettable that such a product is delivered to the customer with the above mentioned deficiencies. Not every customer will have the skills to customize a ready-made device.
Next steps planned
- matching the power output on all bands to the same level
- adjusting the power output to max. 4W@12V
- 80 to 60m conversion, as soon as SW&HW mods are available
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