Shortman

My Feedback: (21)

I periodically leave my transmitter on to run the battery down. I leave the antenna all the way down too and leave it on for about oh 3 hours strait.

I heard this isnt good? Anyone know for a fact?

C_Watkins

My Feedback: (10)

I know for a fact that if the radio doesn't have electronic SWR auto-matching circuitry,
or if the radio doesn't sense high SWR and reduce power output, that it is a "bad thing"
to leave the radio on with the antenna down. Do I know for a fact whether your particular
radio has either of the above features? No... but I'd guess "no", if I was guessing.

The radios' output circuits are adjusted for minimum SWR with the antenna FULLY extended.
SWR usually shoots through the roof, with the antenna down, or with it touching anything.
With a 1:1 SWR, you get maximum power transmitted through the antenna.
With higher SWR, some of the rf voltage/current is reflected back to the final(s).
This is why most radios become quite HOT in the RF section, when you run
them with the antenna down, for any appreciable length of time. Not good at all.
Overheat them for long enough... or often enough, and they will fail some day.

I'll let someone else handle telling you why you also shouldn't take your batteries
down to less than 1.1v per cell or so... but I'll let you know, that's not good either

Shortman

My Feedback: (21)

I have the Futaba 9CAP PCM radio. I run it down to about 8.8 ish

Flyfalcons

Might be a good idea to pull the module out when doing this.

Steve Lewin

As I said before (the last time Shortman asked this same question) it can damage the output stage of some transmitters. I have seen several transmitters with dead output devices because of this. I'm not sure how much additional proof you want (or perhaps you just think I'm lying ).

Taking the module out won't work very well for your purposes because there is very little current drain on the batteries without the RF module. It would probably take several days to drain the batteries.

Steve

bushwhacker

Take care when doing this. Discharging nicad packs too low ( below 1.1volt per cell) can ruin packs. Some cells may become reversed. Use a discharger or cycler to discharge cells. Radio equipment is an expensive item and should be treated with care.

After a recent tragic death in the uk caused by a model hitting a youngster on the head we must be seen to be acting responsibly and share good practice to eliminate these types of accident.

happy and safe modelling

golf_lake

http://www.rcuniverse.com/showthread...757&forumid=27]

Shortman

My Feedback: (21)

Alright, well my Dymond should be here this week so I can discharge it properly now. I didn't know it would be so bad.

rajul

My Feedback: (58)

Shortman, don't do that. You'll burn the RF amp in the module and your range will be reduced. I suggest you do a range check to verify the condition of your module. Use a cycler if you need to drain the batt and recharge. When you're doing plane setup, extend your antenna at least two segments (bottom segements) so that your module don't get overheated.

MHawker

My Feedback: (16)

Short',

Have you ever noticed while you are setting up planes or whatever with your 9C that your module gets very warm? I was setting up a plane and I always extend the lower (largest) segment of the antenna while I do anything.

Even with that, the module gets pretty darn warm. If I extend the antenna further, it immediately starts to cool.

This, to me, shows it's better to extend the antenna (per Rajul's advice at least) while the radio is on.

Mike

Rodney

It is never a good idea to run your xmtr with the antenna collapsed, even just partly extended does not help much. The standing wave ratio (SWR) goes way up and all the energy is dissipated as heat in the output stage. The designers know that this is going to be abused so they do try to make the output stage extra rugged; but, the mean time to failure is cut in half for every 10 degrees C that the temperature rises so you are abetting an earlier failure when you run with the antenna collapsed or even partially collapsed.

MO_Radio_Tech

Just my professional opinion...

Never leave TX power on for more than 5 minutes without antenna fully extended. If you have DSC capability, get in the habit of using it. If not, extend the antenna. You can use a transmitter all day long with the antenna fully extended. It will reach operating temp and stay at that temp.

Transisitors are like light bulbs in the fact that they have a lifespan. This can be decreased if the part is overworked.

Using DSC also uses much less power. Direct Servo Connection. Longer battery life at the flying field.

Shortman

My Feedback: (21)

You guys think I will be all right? I have done this before and havent noticed any problems. For now on I will never do that again lol.

What COULD be damaged if it were to be broken?

Geistware

My Feedback: (16)

SO tell me, is the output stage in the module or in the transmitter body itself? Will replacing the module get you back to your original strength?

C_Watkins

My Feedback: (10)

I believe that the module contains the entire RF circuit on all those transmitters.
It's about the only way for it to be legal for end-users to switch them out.

So yes... proper repair, or replacement, of the module should bring it up to snuff again.

Geistware

My Feedback: (16)

Thanks Mr Watkins!
Where do you fly in Georgia?

C_Watkins

My Feedback: (10)

Oh no... it's a trick question... and I hate trick questions

I'm "supposedly" flying out at PCMA ... though it hasn't been happening lately.

Seems like every time I make plans to fly, it's either raining all day, or a tree
falls on the house, or one of the cars decides it's a fine time to blow up on me.
(Spent this past beautiful Father's day, replacing the tranny in my Lumina. Oh joy.)
If that isn't good enough to keep me grounded, I get called in to work, instead. ARGH!

Anyhow... I hope to break out of the slump, on this upcoming weekend.
I have a Lanier Extra, with my first ever .91 FS up front, just screaming to be flown

I also hope to make it out to visit some of the other clubs in the area... sometime.
Seems like being in Powder Springs puts me in a 20 mile radius of just about everywhere
to fly, at least. I just happened upon PCMA first, and they're a great bunch of guys.
So where do you fly?
I bet it's at least 20 miles from me. Heck, even CCRC is, and I'm IN Cobb county



Just saw Shortman's last post... as for "what will be damaged?"... probably just the module.
Still... that's a *very* important piece... if you intend to actually fly anything

mcwings

The proper way to recycle radio batteries is to remove them from the radio and discharge them at no more than twice the ma rating if they are nicads. nimh batts. at no more than the ma rating. Heat is the mortal enemy of all electronic circuits. By leaving your antenna down, you don't have enough heat disipation for the output stage of your radio. Do not discharge your batts. below 1.1v. You can and will damage the charging capacity of the batt. if not causing cell reversal. Charge your batts. at 10% of the ma rating. Fast charge only in an emergency, and never more than the discharge rate. But be aware that some batts. cannot be fast charged. Not sure what your batts. are. If your batts. are in good condition they should last you a long time.Hope this has been helpful. mcwings (retired electrical engineer) Any questions or comments always invited. p.s.

photoniq

Guys - I hope this is not too off topic but...

I can not afford a discharger etc right now. Is it ok to discharge the battery by leaving the tx on WITH THE AERIAL UP? In all of the posts above it seems that the aerial being down is the real issue.. am i reading this wrong?

Thanks in advance,

phoTToniq

MHawker

My Feedback: (16)

This has been discussed before, but the short version is: You "could" do this but you run the risk of draining your batteries too low and causing damage to them.

It's best to get a discharger or not discharge at all.

Mike

fritzthecat

My Feedback: (4)

First of all, the Futaba 9C radios will autoshutoff before the batteries completely discharge.
Second, why are you cycling your tx batteries so often? Once every 6 months is plenty, once a season is fine too. If you don't want to cycle get a Nimh pack and enjoy longer battery life.
If you absolutely get off on cycling, buy a good battery charger like the Supernova or the Triton.

Fritz

mcwings

Fritz, Thanks for your reply on the rx's. Good info. Now about nicads; Most people use their radios maybe once a week for maybe 3 or 4 flights, then go home and let their radios sit until the next time they want to fly. Then they charge the radio the day before. Their batts. still have probably 50% charge left. (some don't fly as often). After 10 to 15 charges at 50 to 75% of batt life nicads begin to have diminished capacity. (even new ones). Nicads dont have memory, they just don't have the capacity to fully charge. Unless you recycle. General rule of thumb. Even if your radio shows a full charge, that doesen't mean your batteries have been charged to their fullest. I will try to find my info on nicad charictoristics(spelling?) and send it to you. By the way, I use 1600ma nimh for all my tx's and rx's. This eleminates the problem alltogether. As for the Futaba 9C; I don't have one yet. Glad to hear of that feature. Hope to have one soon. Not everyone shares this opinion, thats ok. That's what makes the world go around. Thanks again for the info. on the rx's, I'll look into them. Good flying to you, mcwings

SilverComet

After reading this thread, I decided to extend the antenna when I'm programming my new 8103. However the module still gets kind of warm after I turn it on for about 5 -10 minutes, is this normal?

rajul

My Feedback: (58)

That's perfectly normal. Don't worry........

BillHarris

You could always uplug the RF module or plug in the DSC ("trainer") cord; either way will inhibit the RF output of the TX.