TK-840 Power question

[N4GIX]

SWR is the same regardless of frequency. It is simply a matter of the ratio of the transmit power and reflected power.

Or, putting in even simpler terms, it is a percentage of "wasted power" that gets reflected back down the feed line to your radio. A 1.6:1 SWR equals a 5% loss of power, meaning absent any other losses in the connections and the feed line, your antenna is radiating 95% of the power.

An SWR of 2:1 is the absolute minimum I'd accept myself. Of course to check your SWR you'd need a meter that will work in the UHF range! You simply put the meter in the CALIBRATE position, key up and adjust the needle for full deflection. Then measure your FORWARD power, followed by the REFLECTED power. Ideally you'll see the needle barely move for reflected power.

I'm glad to hear that you have the cable and software. You should be able now to see whether you can connect to the radio and master the rather primitive DOS software... <giggle>

 

[N4KVE]

I'm going to keep my eyes open for a TK-880 mainly because of its ability for FFP...

Care to share? I have 2 880's, & they are great as they work with CPS, but the 840 works just as good. But a problem to program. I wasn't planning to sell any 840's, but I felt bad for the OP, so that's why I made my offer to him.

 

[Josh380]

The software seems basic enough. I already have a ton of stuff ready to write to the radio. I have to say I am impressed with the amount of frequencies that can be programmed into this thing. 8000. Whew. I can't even imagine being able to fill it up. I thought of saying I'd like to meet the man that has all 8000 slots filled up, but in hindsight, maybe not.

 

[N4GIX]

Care to share?

Argh! That's the problem with posting late in the evening. I typed FFP instead of FPP (Front Panel Programming). I don't know "how" myself, but having watched a YouTube video of a fellow doing actual FPP on a TK-880 I have to believe it is possible.

Here: https://www.google.com/url?sa=t&rct...cNC4Drrjte4GEtWdJmW7Hw&bvm=bv.108538919,d.amc

 

[N4GIX]

Josh, honestly 8,000 slots is quite a bit of "overkill" IMHO.

By the way, while it is only possible to scan a single "Group" of the 32 "Systems", it is possible to pre-select a specific "Group" within a "System" that will be scanned. We are not limited to only scanning "Group 1" of each "System..."

For example:
S - G
=====
1 - 1
2 - 20
3 - 5
4 - 16
etc.

I am likely going to program one System with only simplex GMRS frequencies and another System with simplex 70cm ham frequencies.

Other Systems will hold local GMRS and ham repeaters that I have access to.

 

[N4KVE]

That's amazing that the radio can be programmed that way. Good to know. If you're in the field, & don't have a laptop it's good for a quick PL or button change. But the CPS is cheap, easy to find, simple to use, & quick, so I couldn't imagine setting up 10 freq's using the buttons. I'd try to sell your 840, & buy a 880. The last one I bought from a 2-way shop cost me $70.

 

[Josh380]

Josh, honestly 8,000 slots is quite a bit of "overkill" IMHO.

Total overkill lol!

I am likely going to program one System with only simplex GMRS frequencies

That's a good idea.

 

[N4GIX]

Total overkill lol!

Well, in fairness to the designers, for the purpose for which the radio was built - an LTR trunking system - it's not. An LTR system can support up to 250 "talk groups". More than that would require another "System" of 250 Groups.

From our prospective as either ham or GMRS operators though, the current arrangement is definitely not only "overkill" but is rather clumsy. A great majority of the memory capacity is going to never be used.

 

[N4GIX]

I'd try to sell your 840, & buy a 880. The last one I bought from a 2-way shop cost me $70.

Oh, I'm looking for a TK-880 to use in my car. This way I won't have to un-mount the radio for programming any new frequency should the need arise.

I'll keep the TK-840 for my planned use as a "control station" for my repeater. As much as possible I want to keep GMRS out of my ham gear as there's far less chance of getting them mixed up that way!

 

[N4KVE]

OK. Just so you know, while a 450+ TK-840 covers the whole UHF ham band [my 4 do anyways] a 450+ TK-880 does not. Depending on the particular radio, RX will start at 442, or 443. TX goes a little lower. There's a simple VCO adjustment required to fix this. My first TK-880 had this adjustment done by the seller, & works great, but the one I just got from the 2-way shop starts working at 443. OTOH the 4 840's all came from the same seller I got the ham friendly 880 from, so maybe he adjusted them too. Don't know. Also, the heat sink fins are real small, so you will need a cooling fan if your transmissions are longer than 3 words.

 

[N4GIX]

OK. Just so you know, while a 450+ TK-840 covers the whole UHF ham band [my 4 do anyways] a 450+ TK-880 does not.

The TK-840 comes in "three flavors" and the one Hams and GMRS operators want are the one's that have a -1 after the FCC certification number. The two -2 and -3 versions are not capable of tuning down to the Ham and GMRS frequency range.

There is a seller on eBay who commented he didn't know what version he had up for sale. I sent him a note that he has a -1 (which was plain to see from his picture of the label) but even though he acknowledged my note and thanked me, I see that he did not update his listing... <shrug>

I'll keep your commentary in mind when shopping for a TK-880 and be sure to ask the seller if he knows if the mod has been done, else I'll have to research and find out how to do the mod myself.

 

[N4KVE]

I'll keep your commentary in mind when shopping for a TK-880 and be sure to ask the seller if he knows if the mod has been done, else I'll have to research and find out how to do the mod myself.

Most sellers just say "bought at a warehouse sale & know nothing about radios". Here's the Ham mod.
http://forums.radioreference.com/kenwood-forum/308822-how-adjust-vco-get-440-mhz.html

 

[N4GIX]

Thanks! Now I know where to find the info whenever I need it.

 

[Josh380]

UPDATE

So had a great day today. I ordered a 13.6v 10a constant 12a surge power supply, and I've got a kpg-4 cable ordered from China (that's gonna take a minute to get here). The supply is coming from San Diego, so i'll at least be able to confirm that it powers on in a few days. Don't worry, I know not to transmit.

Now I just need coax and an swr meter.

I emailed Kenwood about this issue (before the clarification here) and it's like talking to a brick wall. I told them that it's a tk-840 and they think I'm talking about a tk-840 with a narrowband kit installed. They did say though that once a narrowband kit has been installed in an 840, it will ONLY do narrowband.

 

[N4KVE]

I doubt there's an employee at Kenwood who is familiar with the 840.

 

[N4GIX]

I emailed Kenwood about this issue (before the clarification here) and it's like talking to a brick wall. I told them that it's a tk-840 and they think I'm talking about a tk-840 with a narrowband kit installed. They did say though that once a narrowband kit has been installed in an 840, it will ONLY do narrowband.

According to a source I found here: https://www.google.com/#q=remove+narrowband+kit+from+kenwood+tk+840...

•TK-840 => Wide band only (note: There was a narrow band version (TK-840(N)) otherwise there was a ZKIT-840NB which is no longer available

So, even though I most definitely have the TK-840(N), signal reports I've received from everyone I've contacted have been uniformly positive.

 

[Josh380]

Power supply arrived today. Power on test is ok. It appears there's only one frequency programmed, or the guy who sold it to me wiped out the old stuff and just put one frequency in there.

Now just waiting for the programming cable and gotta get an antenna. Almost there.

 

[Josh380]

One quick question..someone mentioned using a fan for cooling. Will a cpu fan do? There's a nice tapped hole right in the back..perfect spot to mount it.

 

[N4KVE]

As long as there is enough wind circulating to keep it cool during transmit.

 

[mmckenna]

Yes, I think they are 12 volts. Should work just fine. Keep an eye on dust build up, though.