Slightly different concept than your standard EMComm box.

The Emcomm Backpack!
DC to light.  100W.  Can run off of AC or DC or internal battery.



This rig was originally used for working satellites, as it has the split VHF/UHF rx/tx capability.  But after some time, I wanted to put some auxillary functionality in it.
Couldn't figure out whether to do the dual Yaesu batteries or the built in power supply from Yaesu... so in true ARFCOM tradition I decided to do both!
Now the problem was to figure out how to do both.  So lets see what we have to work with.  




(Pictures taken from internet)

Two battery bays, so lets put in one battery and one power supply... easy right?

Well as it turns out, finding a supply that fits in the height to allow the original case to be put on is quite a challenge.

It would not only need to fit in the space allowed (1" tall was the hard part), but it would also have to have the current capacity to run the radio at the full 20w that it can run at from the internal battery connector.
After searching through all the major suppliers of open frame supplies (Mouser, Newark, Digikey, etc) I found this supply from Advanced Power Solutions (APS103VP).  
11 amps continuous at 12 V, and more importantly, low noise and the correct dimentions!

It has the following specs.
http://www.pikpower.com/new%20site/aps_b/pdf_internal/APS103VP.pdf


But to furhter complicate things, you can't buy this power supply from any distributor in single quantities.
After talking to the manufacturer over the coarse of a  few days, I was able to get them to sell me a "sample quantity" of 2 supplies.
(BTW, I still have the other one, new in box, if anyone is iterested in it you can IM me.)

So now with it mounted and installed, I have the capacity to run off of traight AC at 20W, and I can run off of the internal battery.


I have it set so that the "A" battery is actually the internal AC, and the "B" battery is the internal battery.


I can also charge the battery off of my internal supply with the Yaesu converter.  It only requires a few amps at 12v, and is no problem for this small power supply.


And with some standoffs, I can store it all in a standard backpack (with the LDG tuner) along with some wire antennas.



Hope this gives someone an alternative to the orange/OD green debate!


The orange guys may be seen better, the OD guys may look cooler, but the backpack guys are the only ones that are going to be carrying this thing for miles with any reasonable comfort!!!

Need Moar Green

Seriously, Very Nice btw, Linked in the EMCOMM Box Thread

ETA: What type of antenna are you considering?

Nice!

Don't know yet, any suggestions for small wire antennas would be appreciated.
I've got a slingshot, lead weights, and fishing line to get them where they need to be.

Its not orange....

I like the backpack setup that doesnt necessarily need to be put down and set up to use like a conventional box.

any idea to run a vertical for VHF/UHF while "foot mobile"

 

Window line slim jim or coax dipole, on some kind of support like a fishing pole or fiberglass off road flag pole mounted on the pack.  Wire on the pole plus tuner and drag line for 10 meters.  

That could be done pretty easily with a standard coil loaded 5/8 wave whip.
No ground plane needed.  (Something like this...http://www.theantennafarm.com/catalog/index.php?main_page=product_info&products_id=3211)

To get to 10m would take some effort, but VHF isn't too bad.

Few options listed here:

Clicky the Linky

Very ingenious!

I love the hardline coax between the radio and tuner...

Very cool.  The 897 seems like an under appreciated rig.  20w is a good power level for a "field" radio IMO, regardless of the traditional "QRP" 5w designation.

One question, 11A seems like a lot of amps for a 20w transmitter.  That should get you to 50W really.... just curious if that's all that was able to be found, or what was the rationale.

The 897, when switched to run off the internal power, backs down to 20 w.  I don't know the exact details of how it does that, or if it can be overridden.

There's always someone that has to be different.  



Great setup... and you're right, it would be easier to carry around.

Yes, the 20W is the limit off of the internal power connector (where the battery would connect.)  It is software limited in the radio.

I could use the external power jack and the output of my power supply to get to 50W, but it would be on the edge.
22Amps is drawn during 100W operation so 50W on 11 amps is probably pretty feasible, but I'd likely only do it in an emergency setting.

The 897 can also be dialed down to 5W if you wish to do traditional QRP operation.

There are some guys out there that put a few supercapacitors on the output of their supplies to allow them to operate 100W on SSB,... I'll see if I can find their website later.

One of the benefits of being a nerd is having a nerdy job that has scrap semi-rigid coax lying around.  

I'd like to find the caps they are using,  I have a 200w amplifier that I think I'm getting power starvation on and would like to try using that technique to boost the voice peaks on SSB.

I don't know what model they are using exactly, but if you know how to calculate equivalent capacitance, you should be able to figure out some equivalent and purchase the caps here.
More super caps than you want to look at
To anyone thinking of doing this, make sure you understand what you are doing.  This many Farads is not something to play with lightly.  You can kill yourself with this much energy!

Found the guy selling the supply I was thinking of.  It is Gamma Research
They use 5 caps in series at 25Farads each for an equivalent of a 5 Farad at some 13+ volts.  It is then powered off of a 5Amp supply.
Works fine for low duty cycle CW or SSB.  Here is a review of the internals and what is going on.  review of gamma supply

I could probably do the same thing to my rig as I have some extra space in there.  Probably won't though for now.. too busy working on installing my mobile.

The 857 is very similar, but uses a brown lead that when connected to ground, limits the power.  On my backpack rig I considered all options and decided to leave the power selectable.  By not grounding the brown lead on the connector, I have full options on power which is only limited by the coupler (60 watts ssb or 20 watts rtty) and the battery 16 ah lipo.  I already found this useful when I wanted to get a little bit better signal out on 80 with a 21 foot wire by using 25 watts.  

Good job on the build!  The backpack rig is the most portable and instantly usable  emcom solution in my opinion.  I am afraid mine is green though.

thread lacks any sort of orange but hardline with SMA's makes up for it.

ar-jedi