uniden pc78xl

[AE5RD]

limiters

I think alot of the reason that some operators and techs and hams want clean radios is that a radio full of harmonics do tend to bleed into other channels including other bands. I was trying to DX one night and i was using a Yaesu 101b on 38 lsb. I turned on the old Firebird 500 for some kick. What i didn't realize is that i was wiping out 10 meter communications in my area. One of my fellow ham operators contacted me on 70 cm and let me know what was happening. Wow I didnt realize my equipment was so dirty. Now i would like to get a monitor scope to check my transmissions so that can stay within my bandwidth. I still want to kick butt on AM and ssb but not at the expense of everyone else. If i could clean up my radio and my amps I might stay out of trouble and I won't have that knock at my door. I bet my old tube amp is bleeding all over the place. I find that i no longer use my 16 pill anymore cuz i have better luck with a base antenna beam.

 

[speedracer6g]

I agree that cutting limiters is bad. If you have a peak meter like a bird 43p you will see clipping your limiter does not get you more pep power. it will increase your avg power. this is because your avg power looks higher to your meter because you have a square wave instead of a sinewave. you tech guys know what i am talking about. So anyway put you limiter back in and set your modulation with a plane old scope nothing specail and set you modulaton to were you have a smooth waveform with no clipping. theres my two cents

Mike

Diberts Electronix www.mynovesecurity.com

 

[Sci-Fi]

Missing Diode? ... thanks for any help ahead of time

I have a brand New Uniden PC78XL i'm looking for the limiter on this radio. I like crusty audio at times... I'm going to try installing a switch for the limiter so i can have it on some of the time. Problem is I'm getting conflicting information from 2 different forums.

In the link below you find this post...
http://www.radiomods.co.nz/forum/viewtopic.php?f=2&t=1750

by ramblingman » Saturday 19th Jan 2008, 14:23

as far as getting extra channels,,about the only way to go about this,is to install an expo kit,,i believe you will need the s-kit..but you can get extra swing and modulation,fairley simple mod...remove jp-17 which is located on the left rear corner of the pc board.it will look like a staple.install a 220 uf at 16 volt dc radial mount capacitor..remember install the capacitor with the negative leg towards the final..then flip radio over and install a 100 ohm 1/2 watt resistor across the same solder connections as capacitor..then turn vr-5 fully clockwise,this is your amc adjusment..in otherwords it increase your audio..some will tell you to clip d-9 which is the modulation limiter,but i dont recommend this,,because it will muffle up on close by stations.also some may tell you to jumper out the anti-spiking diode..dont do it,,it will cause premature final failure...i believe this is d-8 in this preticular radio.................good luck
===============================================

He mentions that the limiter is "d-9" in the post. But i looked everywhere in the radio and to my surprise there is no D-9 anywhere on the board i have... or at least can see.
Than in this very topic page 1 someone mentions D-11 diode eleven being the limiter. I can see D-11 on the board down an to the left below the VR-4 pot. So the million dollar question is which one? i don't want to take out the wrong one, so can anyone explain these differences in opinion? Could it be that i missed it? I'll take a pic and post it later when i get a chance if someone knows where i could have missed "D-9" please let me know. Any help is much appreciated.

Thx. _Nick_ aka. Sci-Fi :bdh::bdh:

 

[Onelasttime]

I always thought it was funny that someone would cut limiters and then have to turn moc gain down.

 

[Onelasttime]

So, a clipped radio with the mic gain set to the same modulation level as an unclipped radio with a power mic will sound bad?

It's all in the operator.

My clipped Grant XL is set to noon-1 O'clock. Sounds fine.

I know this is an old thread but I could not help myself. Why in the heck would anyone want to clip a limiter than turn the mic gain down! Just stop and think some deep thoughts on the idiotic idea of clipping the limiter then turning down the mic gain.

It never fails people that do this spend more time trying to get their audio right than they spend actually talking on the radio to other people. If you bump the knob you're now splattering and getting feedback and squealing on key up. If said knucklehead also has talkback on the unit the above is even worse.

I should be quite if too many people listen to my rants I will not be able to key over them with a stock radio or with a tiny amount of power while they are running huge sums of power!

Sadly though I am getting to old to listen to knuckle draggers with craptastic audio and splatter boxes!

AGC is the best thing that ever happened to radio and defeating it or making it harder for this circuit to work will always hurt you in the long run!

I have never had a radio that I could not run the mic gain full tilt. Likewise never had to touch the mic gain when changing out mics.

 

[jon666]

you cant fix stupid.

 

[Onelasttime]

If people want crusty audio they can buy a cheap stereo and cheap headphones listen until their ears bleed.

Since you do not talk to yourself over CB who cares what you like!!! Maybe the people forced to listen to you would prefer to actually understand what you are saying. Maybe others do not want to hear your splatter box 6 channels up and down.

This is the type of selfishness that ruins everything!!! It ruins CB, driving, internet, politics etc.....

 

[Onelasttime]

P.S. Idiots should not be allowed to own a nice radio like a NOS/NIB Uniden PC78XL they should be forced to own POS radio's preferably ultra modern POS radio's!