'Manpack' VHF Project Idea

[NoiseBoy]

Im hoping to do my foundation licence asap and whilst browsing the waters and stanton website i came across an offer of a Yaesu FT7800 for £160 (ex vat)

As i cant really do much from my QTH i thought a fun project would be to make a portable battery powered rig with a whip aerial that i could carry on my motorbike in a backpack.

So i wanted to get some opinions as to whether i would get out much with a portable rig on a small whip aerial, I could build in a DC supply socket and external SO-239 socket for use at home. Is this a good radio, it seems pretty darn cheap to me but it is now discontinued.

Any rambling thoughts welcomed, Im going to start putting together some dimensions and weights together to see if its worthwhile. would the radio be worth much for selling on afterwards if it doesnt turn out so well? Maybe i should hold out and spend a bit more when i can on a multiband HF & VHF rig that i can use at home and on the move.

-Paul

[fez]

A standard VHF vehicle mobile whip should work a treat. Especially if you get up high.
Performance would be increased with couple of counterpoises if the manpack hasn't got much metal.

If you want something rugged and comfy you could look at basing it around this Mil DPM radio backpack:


http://cgi.ebay.co.uk/NEW-Army-Issue-Ru ... 587e1782a8

I have 3 of these, One as a general backpack and 2 others for Mil hf radios. And I can vouch they are very confy and strong.

They are about £25-30 posted new on ebay.

[JamesA]

Yep cracking bags those, ive got one as well and it would be ideal for what you are planning.

7800 is a nice radio, i have the 7900 which is the same but with 6 and 10 as well. Another option would be to pick up a really cheep 2nd hand 2m rig on ebay which you could hack about to suit your needs, rather than worrying about damaging your nice new radio.

Mobile whips would work well i should think, but you could also make a 2m dipole and mount it in some 15mm conduit pipe. would be easy then to use horizontal or vertical if you upgraded to a SSB rig in the future. Or how about a nice 3 element beam?

http://mw0idx.co.uk/idx3elementyagi.html

I made one and all the elements can fit into the boom for easy transport.

[skunkybob]

I use a five ele 2m(works on 70cms ) yagi (in a SOTA build style), 7m fibreglass pole and occasionally carry a 12v 7ah SLAb( if a SOTA activation I just use the internal battery in the FT 817), I use a FT 817 for SSB on VHF/UHF and on 2m FM, I have a Puxing 888 vhf with 2 batteries ( I have the UHF version too), go high and be surprised how far you can. If I can haul this plus my food, drink etc up a hill then you young 'uns could too.....even a HF inverted vee ( or what have you) built with copper wire used in conjunction with the pole, great fun....plus exercise and great views...

http://farm3.static.flickr.com/2554/377 ... bd259b.jpg

Short mast due to loose section that day...worked into North Wales on 2 1/2 watt ssb. Faslane naval base is just down the west side of the hill....

http://gm7something.wordpress.com/2009/ ... rip-25709/

[skunkybob]

A better pic of the beam....

[Yeti]

Does the 7800 have a removable front?

Once I get my hands on an Icom 706, I'll make something like this up - and mount the front panel on the shoulder strap.

[5thElement]

The FT-7800 does have a removeable front, you need the seperation cable though as the cable that connects it is only about 4-5 inches long.

[NoiseBoy]

I ordered the radio today from waters and stanton. FT7800 plus mounting bracket plus remote kit for £170 delivered.

Ive started looking into the power options. I originally planned to use a sealed Motorcycle Battery but as ive done alot of research in the past into converting a motorcycle to electric (still on the drawing board) i thought i would take the plunge and go for Lithium. The weight and space savings are considerable.

There is a popular cheap 12V battery that alot of the media people are using for portable monitors on ebay for £30 Here. 9800mAh and weighs 400g. Dimensions are 115mm x 53mm x 33mm

Compared to an 8Ah motorcycle battery which weighs 3kg (152mm x 88mm x 106mm) the space and weight savings are significant. Also the lithium pack has a built-in BMS meaning i can have a simple power socket on the case and a switch to either run the radio from mains or charge the internal battery from the same 12V power supply.

How crucial is power supply stability in radios? Because i can modify some old designs for power smoothing circuits that i used for audio projects if necessary.

[G0TVJ]

The FT-7800 does have a removeable front, you need the seperation cable though as the cable that connects it is only about 4-5 inches long.

I think you can make your own. The cable for the 8800 and 8900 is standard flat 6-way with crimp on plugs. If the 7800 is the same you can have a custom-length cable for a few pennies at Maplin (plus the cost of the plug-crimper if you don't have one )

Neil

[fez]

The FT-7800 does have a removeable front, you need the seperation cable though as the cable that connects it is only about 4-5 inches long.

I think you can make your own. The cable for the 8800 and 8900 is standard flat 6-way with crimp on plugs. If the 7800 is the same you can have a custom-length cable for a few pennies at Maplin (plus the cost of the plug-crimper if you don't have one )

Neil

They are about £5 on ebay for the lead. Hardly work it.

[G0TVJ]

The FT-7800 does have a removeable front, you need the seperation cable though as the cable that connects it is only about 4-5 inches long.

I think you can make your own. The cable for the 8800 and 8900 is standard flat 6-way with crimp on plugs. If the 7800 is the same you can have a custom-length cable for a few pennies at Maplin (plus the cost of the plug-crimper if you don't have one )

Neil

They are about £5 on ebay for the lead. Hardly work it.

That's true, but what about the warm glow you get from having made your own ?

I use my 8900 in the car so it's also handy to be able to make a cable that's exactly the right length for the job and not have to coil it up and stuff it somewhere.

Neil

[JamesA]

There is a popular cheap 12V battery that alot of the media people are using for portable monitors on ebay for £30 Here. 9800mAh and weighs 400g. Dimensions are 115mm x 53mm x 33mm

Looks like quite a nice pack that. I have a 4.6ah 12v nimh radio controlled car racing pack that i use to run my 817. About half the size and weight of the equivalent SLAB.

[NoiseBoy]

Right ive ordered the power back. Once they arrive i can start doing more detailed plans.

The biggest issue is finding a container for it all. I thought about a pelicase but they are very heavy and also expensive. Plus much larger than the internal volume so not great for a bag.

I saw a 'key box' today which although not really suitable it gave me an idea. Its a metal rectangular box that hinges on the shorter side and has a lock opposite so convenient for access inside. Having said that i hope to wire it all up so that everything is controllable from the outside and i wont need access.

Im thinking though it would be useful if i fixed the remote panel mount on the outside and left space inside so that i could keep the panel inside the box when not in use to protect it. And it would also allow me to detach the front panel and mount elsewhere for convenience.

[JamesA]

I have a small aluminium flight case from maplin. Originaly i bought it to build as a portable station for my 817, but it ended up as a tool box
It would fit inside the ex mil radio rucksack i think, give good protection and you could mount connectors through the case.

http://www.maplin.co.uk/Module.aspx?ModuleNo=222024

[Guzzy]

The Americans have been playing with porta-paks for 'emergency comms':