The Little MMR-40 Multimode transceiver
Thursday, November 22, 2007 9:14:31 PM
My impressions on this rig are definitely favourable. The kit arrived within seven days of having been shipped. Considering that it had to clear customs, that is pretty good.
This is a complete kit, right down to the plastic enclosure that was supplied. I printed off a copy of the assembly manual and started building. For me, the first thing is to sort and check off all parts. Nothing was missing. All items were packed with care. This is a well thought-out kit. The manual, while not a step-by-step construction manual was adequate. Even a beginning builder (if capable of following the directions to a T) will be able to assemble it.
The only issues I had were of my own making (misread the value of a capacitor) but the error was caught before the kit was completed. There is a yahoo group (http://groups.yahoo.com/group/mmr40owngrp/) with great information on various stages of the build. Those considering this radio are advised to join the group and read the posts. Doing so will pinpoint areas where some builders had difficulty.
My rig powered up with no hitches and full output. I chose not to use the supplied enclosure, as I wanted more room to add some accessories. I used a larger speaker hoping it would give me better audio and made some minor circuit modifications.
How does it work? The answer to that is SURPRISINGLY GOOD. The receiver is sensitive and if using it for cw there is a narrow filter that works well to reduce broadband noise and adjacent signals. SSB signals are easily tuned (lower SSB only).
Output power is 7 watts or so when using a 13.8 volts supply and about 4-5 watts (according to my watt meter) when using a 12-volt battery, more than enough to make good solid contacts on cw. I have only made one local contact on SSB and that was very weak (both ways) so this review has nothing conclusive to report regarding this mode. My received audio was readable and the microphone used on my end was a $1.00 mike from the Dollar store, so take that report with a grain of salt, as it is tough for me to imagine good audio from such a cheap mike.
The transceiver uses a PTO for tuning (and you get to build it). With careful adjustment, it will tune almost the entire 40-meter band. I suspect by using a little ingenuity, one could get full band coverage however I am primarily interested in the lower band portion so I have not bothered to try.
I gave this review a rating of 4 rather then a 5 because of the PTO and that because I find the PTO rather slow in tuning and not as mechanically stable, as I would like. Mechanical stability was improved by wrapping teflon tape on the threads of the brass rod however I suspect this is a short-term fix. This may be an issue with my construction rather than with the design, I do not know. Certainly the PTO is electronically stable and I notice no drift during warm up or during operation. Others have mentioned that they have found a small amount of drift during warm up however because I used a somewhat larger enclosure (plus a metal one) I suspect that heat is more easily dissipated then it may have been with the plastic case as supplied.
Would I recommend this rig? Darn right. For someone interested in a qrp radio with all these features, the price and quality are certainly right and you should be quite satisfied with the end product. In addition to using the rig on cw, I plan to try mine on psk31 but am currently building another kit so that may have to wait till fall.
I want to add to my previous review of this excellent little rig. I added a digital display for frequency readout and am very pleased. (Kd1jv was selling these displays but I believe he may be sold out. The word is that Doug Hendricks will shortly be adding the display kit to his list of nice QRP products -- http://www.qrpkits.com/). I had not been using the rig and I think I had determined that the reason for that was the slow tuning of the PTO however I realize now that in truth, unknown to me I was finding the lack of frequency readout to be putting me off.
Now that I can easily determine where I am in frequency I find the radio to be far more enjoyable to use. I have an SW 40+ that has no frequency readout but it has a single turn potentiometer for frequency control and by marking on the cabinet I can see at a glance where the rig is tuned. With a multi-turn system such as the PTO one cannot do that. The digital dial makes all the difference. I know it is hard to understand. HA HA
I also modified the radio with an audio output jack for use with an external speaker. I have a speaker with an active audio filter built in to it and the improvement in audio is amazing. The lack of AGC is far less noticeable when using the outboard speaker/filter combo. Now the MMR-40 is easier to listen to than my Kenwood radio with a far quieter receiver that still pulls out the weak along with the strong.
After all is said and done this rig definitely deserves a 5 rating.