SWLing Post readers: I originally published the following post on QRPer.com. I thought I might share it here on the SWLing Post as well since we’ve so many readers who regularly use compact battery packs, earphones, and portable speakers. I’m looking for some advice as I build a super-compact SOTA/POTA field kit around the Mountain Topper MTR-3B. If interested in helping me sort this out, read on:
I received my Mountain Topper MTR-3B last week, and I’ve already taken it on a POTA activation.
Last weekend, I decided to break it in on a POTA “two-fer” site: Hampton Creek Cove State Natural Area (K-6246) and The Overmountain Victory Trail (K-4577) in Tennessee. Hampton Creek Cove was actually an ATNO (all time new one) so it was a trial by fire!
In short, the MTR-3B was marvelous. I’m so impressed.
As I mentioned in a previous post, I’m building a full SOTA/POTA activation kit for the MTR-3B. I already have a kit built around my KX2 and I don’t want to “borrow” any items from it (so I’m not surprised later in the field when an item is missing).
For this activation, I powered the MTR-3B with this inexpensive 12V battery pack a friend recommended on Amazon.com (affiliate link). The battery pack is almost identical in size to the MTR-3B and works perfectly. The battery, charger and cable all set me back a whopping $25.
I also used my Whiterook paddle (which needs new paddle arms at this point) but that will soon be replaced with a set of N0SA portable paddles I recently ordered.
Since the MTR-3B has no volume control, I used a pair of 20 year old Sennheiser earphones I bought when I lived in Munich. These have been in a drawer for ages because I now prefer using in-ear earphones with silicon earpieces for better comfort and sound isolation. But the Sennheisers have one thing none of my other earphones sport: in-line volume control.
While the earphones worked well for this activation, I’d still prefer a set of in-ear earphones with in-line volume control. Any suggestions from MTR-3B owners? Also, I’d like a compact amplified speaker with volume control to carry as an option when needed. If you can recommend one, please comment!
I’m writing an article for The Spectrum Monitor magazine about portable power later this year. I noticed that a number of MTR-3B owners swear by 11V rechargeable Lipo cells that are used in the RC and drone markets. Many have a similar compact form-factor as the common 9V battery. I understand, however, some of these cells need special chargers and equipment to balance them.
I would appreciate any and all information about these batteries.
In the meantime, Rich (N8TGQ), recently shared a pic of his Mountain Topper portable pack. Check it out:
I think it’s brilliant how he’s mounted everything on a compact plastic cutting board inside the case. Rich says that what he loves about this set-up is that everything is there, ready to go–simply plug in the antenna!
Please comment or contact me if you have any suggestions as I build out a compact MTR-3B kit!
The future of batteries looks very interesting. One company plans to bring radioactive batteries to the market very soon. Considering that the half-life of carbon-14 is 5700 years, these batteries should last very long time. Once these batteries become affordable enough, perhaps we don’t need chargers any more.
I purchased a pack very similar to this a few years ago (sorry about the aliexpress url):
Can’t beat the price. A 3S lipo is a bit low voltage for many radios, but my HB1B is speced down to 9v, so the radio is happy with the full voltage range of the 3S. Some other radios might work better with 4S if they can take almost 16V at the high end of the charge. I’ve never managed to run it down, an 18650 pack is a lot of capacity for my radio -hours of use. Physical protection is required in this case, but this allows the battery to be fit into a more multipurpose housing. Keep in mind that any lipo can burn up if damaged or during charging if faulty or overheated. I charge it where it won’t do any damage.
The battery brand name Liitokala is very surprising. The word liitokala is Finnish and it means flying fish.
You may pick a pair of these earbuds from Sennheiser
those have built-in volume control and don’t need a battery, so may fit the bill and avoid dragging power from the battery pack; an alternate solution would be picking one of the (many) available LM386 based amplifier boards, like for example (just one from the bunch)
place it into some suitable enclosure hosting the amplifier and a speaker, the box will have the volume control, speaker grid, headphones jack (excluding the spkr) and power jack (excluding whatever internal battery); at that point you may use it with whatever headphones/earplugs even if they don’t have a volume control
Also, consider the idea of adding a (removable) velcro strap belt to the key/paddle, that will allow you to tie the key/paddle to your leg and use it even if there isn’t a suitable table/support 🙂
One more thing.
I am not currently using a Lipo battery, but I am using the following with NiMh batteries:
Battery Holder, 10
I also use these in conjunction with the pack:
5pack 9v Battery Clip with 2.1mm X 5.5mm Male DC Plug
Onite 2pcs DC Plug Tips Female Connectors to Male Jack for PSP 2 3 4(5.5×2.1mm to 4.0×1.7mm)
This has also worked well for me. Hope this helps 🙂
When batteries are fully charged, I use 9 batteries instead of 10.
Hello, I have the same transceiver. I don’t have suggestions for the battery as I have the same one, but I have a couple of suggestions for the volume control as well as a speaker;
Inline Volume Control for 3.5MM Headphones
Rokono BASS+ Mini Speaker – has built-in volume contol
Hope this helps 🙂
I very much like to use my Quad Driver In-ear Headphones by 1MORE. The audio quality is fantastic and they’re manufactured well above the standard of similarly priced in-ears. My pair performs well for use-cases such as high resolution audio players, travel, many types of radios including shortwave receivers and connecting via lightning to 3.5mm adaptor on my smartphone. Audio quality is quite surprising. If you like warm sounding deep bass and comfortable ergonomics for hours of use, these might tickle your fancy. Also they ship with a durable case, many different sized ear adaptors and an airplane compatible connector. The best thing about these in-ears is by far the Kevlar reinforced cable. It doesn’t tangle. What I mean to say is… “It doesn’t f#@$ing tangle!” Why other manufactures don’t employ the same features for cabled earphones beats me. I guarantee for all the readers of my post; These are the best cabled in-ears for the price, period. You won’t be disappointed. Happy hunting!
Regarding the headphone part of the post, I have been using Etymotic in ear ‘phones for quite a while for both music and radio. The thing I really love is the fidelity and isolation (I drive a Lotus Seven so external sound isolation is important) that puts the music (or radio) right in the middle of my head with amazing fidelity and isolation. I haven’t compared prices in a long time since I’ve settled on these (mine are high end music), but for radio the lower ‘range’ devices should be adequate and affordable. And they are very light, and quite rugged.
My two cents worth….
So excited to see that you were hiking the Hampton Creek Cove trail. The hike from the West up to the ridge is rugged. Lots of cow pies, and the last time we did it in winter the wind was strong. Good brook trout fishing in the creek on the way up. Great combination of ham radio and history!
It’s a gorgeous area. We hiked up to the end of the pasture. We would have kept going up the trail (even though it was really over-grown) but we were short on time and our dog (Hazel) decided to roll in one of those cow patties you mentioned. We had to turn back. Fortunately, we had some biodegradable soap, so I washed poor Hazel in the creek! All this this excitement and I left my EFT Trail-Friendly antenna in a tree. We’re considering going back tomorrow to see if it’s still there. It was a favorite antenna so I’d hate to lose it. 🙂 Then again, it takes us about 1:45 to get there, so it’s a commitment. Although a beautiful drive!
I have a little 3.5mm splitter with a small pigtail and male 3.5mm stereo connector on one end, and two female sockets on the other end. Each side has its own volume knob. Also gives you a line to record. Then use your favorite headphones. I think i got it at an airport
Something like this though this is not it.
Great idea! Thank you, Patrick!
Forgot to add, one of the big advantages of LiFePO4 batteries is their charge/recharge life cycle. You can expect a useful life expectancy of 2000+ charge cycles vs. the 200-300 charge cycles from LiPO batteries.
They are amazing and my choice battery. In this case, I wasnt something even smaller than a 3aH 9V LiFePo battery, hence the Lipo option.
I’ve had great success using Bioenno’s LiFePO4 batteries:
I know other hams have had great success using these batteries and speak very highly of this company, its products and their service. Just search around YouTube for examples.
Yeah, I’m a massive fan of Bioenno batteries! They are wonderful. In this particular case, I’m looking for something even smaller like a Lipo battery.
I notice Bioenno also sell these:
Would 3 of these in series still be too big?
I think this is what’s inside their 9V 3aH pack which would be a better buy because it also includes the charging circuitry. It’s not that big and may be an option for sure. I was really trying to find something about the size of a typical 9V cell.