Noise toy box design questions

[Cutlass327]

Well, the convoy and one PP1 worked with no problems inside the 88 for years. I just thought it'd be handier to have them external, and since I was already going to make a box to run one mic on both radios anyway, I figured why not just put the modules in that box too.

I thought about the possibility of the talkback feedback issues, so I turned the echo switch off on the 88 which turns off the talk back, and watching my modulation output I still see it squeal.

I added a ground from power plug to shield, and it made no difference I had thought about the cap across power, haven't done that yet. Any caps across mic socket pins help? I know there are some inside the radio across a couple pins...

And honestly, if you don't like them, why bother reading the thread - the title gives away that it is something you don't like. Why clutter the thread?? Just because I like a great sounding radio that I can play around with others once in a while, doesn't mean that it is a heap like some have implied.

 

[sunbulls]

I favor the problem solver approach. It doesn’t matter whether you like noise toys or not. Why? It’s because similar issues often arise with external mic preamps and equalizers.

 

[Handy Andy]

The way I look at it, deals with the post I made earlier...

That was just for the foil layout - they made several changes at various levels - ranging from Resistor values, Cap values - Routings and even how to route the audio thru the Mic jack...

So you say you had the best luck with the 88 - ok, look at it's construction then compare it to the others - I was only trying to show you a method I would look at this as.

Pics Courtesy of CB Tricks...

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Note that Pin 4 isn't even used...

Now for the 939 there is a different strategy...

​

Now pin 4 is used for a keying circuit.

So with the above in mind, choose your best radio for the job, (Sound or lack of Squeal or otherwise tone) and MODIFY the other one as much as possible to the original design you wish to keep - right down to the cap and resistor values used in the radio.

Since both use the 4558 chip just "tweak" values as needed to meet the other radio. This may also need to include the AM regulator section too - because of the DRIVE level the preferred design offered.

This is also why I mentioned "bonding" the Mic toy box to the radios as one unit - if possible - or at least make a setup so then the bonding can occur easily enough so that the radio case and mic box are sharing the same shield level potential.

 

[Slowmover]

me either no toys beeps or flashing lights for me ever

It’s all about timing.

There are days you’re dragging along westbound on IH20 across the 100-miles of the D/FW MetroHex. 106F and the sun thru the windshield is killing the AC. No choice. Worst traffic of the day. Will take well over two hours IF all goes well (does it ever?).

And tired of the same Goody Two-Shoes on air correcting other drivers. Never his fault. Anything. He’s spotless.

Can’t turn the radio off. If an alternate route has to chosen, need an immediate heads-up on the problem.

Kick the footwarmer awake. Ask Goody a question. Use everything from Roger Beep to endless echo to Robot Voice to mock him. (“What? They wouldn’t make you hall monitor in elementary school?”). Corner him on his mistakes. The logical inconsistencies. Finally, is he a Christian?

1). Irritate the crap out of him. 2). Tarnish his sainthood. 3). Bring humility around. 4). Admit to same. (Now that we’re all brothers in Christ, please SHUT UP).

Sometimes works. Since he’s out of effective rifle range, this’ll have to do.

Turn off for another four months.

Did I go and buy such to use it? Already on the radio. Some extra fun.

My objection to noise toys is not knowing how to use them. Well-chosen moments with the right sound or clip can be damned funny. I’ve cracked up a number of times when someone else hits the switch.

The funniest just may be one member of a tribe making fun of another with pre-recorded cartoon or movie voice clips.

Granted, the stupids go out and buy one and screw it up every time.


.

 

[Cutlass327]

The way I look at it, deals with the post I made earlier...

That was just for the foil layout - they made several changes at various levels - ranging from Resistor values, Cap values - Routings and even how to route the audio thru the Mic jack...

So you say you had the best luck with the 88 - ok, look at it's construction then compare it to the others - I was only trying to show you a method I would look at this as.

Pics Courtesy of CB Tricks...

View attachment 27084​

Note that Pin 4 isn't even used...

Now for the 939 there is a different strategy...

View attachment 27085​

Now pin 4 is used for a keying circuit.

So with the above in mind, choose your best radio for the job, (Sound or lack of Squeal or otherwise tone) and MODIFY the other one as much as possible to the original design you wish to keep - right down to the cap and resistor values used in the radio.

Since both use the 4558 chip just "tweak" values as needed to meet the other radio. This may also need to include the AM regulator section too - because of the DRIVE level the preferred design offered.

This is also why I mentioned "bonding" the Mic toy box to the radios as one unit - if possible - or at least make a setup so then the bonding can occur easily enough so that the radio case and mic box are sharing the same shield level potential.

I had never installed any solely in the 939, so no idea if that would make a difference. The 88 is the one I am getting the feedback issues from. I think I may remove the modules and see if the basic Mic "splitter" design causes issues.

As for bonding, the issue there is that the box is plastic. I couldn't find an affordable metal one the size I needed on Amazon. Currently on limited income, and already spending more than I should with this hobby. I have a year and a half of college to go, then finding employment in my new field, before I can 'safely'(?) spend more. Doing this is just something to amuse me and keep me from spending more time and money on the Jeep.... I have debated on the old "wrap it in foil" trick to test...

 

[Handy Andy]

I can understand and relate to that...

Best advice I can give is - finish college - the world doesn't care for anything less -these days.

But...continuing on...

I had never installed any solely in the 939, so no idea if that would make a difference. The 88 is the one I am getting the feedback issues from. I think I may remove the modules and see if the basic Mic "splitter" design causes issues.

As for bonding, the issue there is that the box is plastic. I couldn't find an affordable metal one the size I needed on Amazon. Currently on limited income, and already spending more than I should with this hobby. I have a year and a half of college to go, then finding employment in my new field, before I can 'safely'(?) spend more. Doing this is just something to amuse me and keep me from spending more time and money on the Jeep.... I have debated on the old "wrap it in foil" trick to test...

No, don't do the foil thingy - it'll look like hell and using non-ferrous metal isn't true shielding like ferrous or even copper cladding - which even a simple soild single side copper cladding boards arragned as a box soldered on edge can work better than aluminum foil.

But I digress.

The only reasons I was trying to bring up is how the DX88 versus the 939 designs were/are different - so you'll encounter some quirks with the problem of making the design work well with another.

IT is not just in shielding that this squeal may occur - there may be other reasons - that's why I pointed out that the 939 sends POWER across to Pin 4 while the DX 88 simply doesn't use that pin for anything.

So, if you research filter designs you may come across some that are called Ripple - they help clean up power supply "glitch and noise" and send it to ground or to another capacitor that is used for Equalization and Emphasis. You have these in your Audio Amp circuit and even with the AN612 used in SSB. They take off noise and RF on lines to leave the lines "cleaner" - but comes at a price - as with your issue with squealing - or as tonal effects that many try to tweak out..

 

[Cutlass327]

The thing I wonder though, is pin 4 is Rx, so it it not used anyway when keyed up. How would that affect the mic signal? Pwr/gnd of mods are to power plug, audio is to pin 2, and a wire is run from plug gnd to pin 1. The PP1 has its own switch, and Convoy is wired to Tx (Pin 3).

Foil thing makes sense. I just thought a quick and dirty test to see if it made a difference. looks isn't an issue for that.

 

[dss56]

Did the squeal ever get resolved know an old post but having same problems with a noise toy box that squeals with high power.
plastic box
4 pin cobra mic wiring.
low regular power but if an amp is used then the squeal/rf feedback.
Anyone find a fix for this problem??