Two Tone signal input ?

Rich McCabe

I recently took delivery on a Telepost LP-500.  I need to connect the two tone signal from the LP-500 to my Flex 6500.

According to the Telepost manual if you use a mic input you will probably have to attenuate the signal and possibly isolate it with a galvanic transformer.

I thought I would try wiring it to pin 1 of the accessory port. This worked expect I can only drive the rig to 1 watt which has little value.

From the manual.

Test Tones: Audio output for built in test tones. 3.5mm mono. Connects to the MIC or LINE input of the rig. An attenuator will be needed in the case of mic input, and possibly galvanic isolation (transformer). Interfaces designed for a sound card based RTTY setup can work for this, but the existing commercial ones that I have tested have some deficiencies.

Line Level… Most rigs have a high Z (10K) line input designed for sound card based digital modes. These inputs work well for the LP-500 test tones. One some rigs they are labeled as line inputs, and have dedicated RCA or 1/8” (3.5mm) jacks. On some rigs they are part of an ACCessory jack or a RTTY jack. These are generally DIN type connectors. Consult your user manual for specifics.

So looking for suggestions on how to do this.  I am using the balanced line input for audio so have that tied up.

k3Tim

Pin 1 looks correct.
Q1:  Does the "Vu" meter show a reasonable level?

Q2 Is the LPM set to output line level?

ka7gzr

I also have an LP-700. I directly input mine to the MIC input. The Mic level does not need attenuation  for the tones in my case.

Larry _ NY8T

This is what I did for my Flex 6500 and LP-700. I am getting 80 watts out with the 2 tone.

Rich McCabe

Tim,  No the meter does not show reasonable level when connected to pin 1.  It does however on the balanced input.  I don't think Telepost tells you what the actual output level is. I could be wrong.

James,  I might have to use the foster connector for now.

Out of curiosity what does your two tone look like on your Flex?

Playing with something like this is new to me. But this does not look good?

Larry,  as I said above I tried Pin 1 but even with radio power level at 100 watts the two tone will only drive the radio to around 1 watt.

Larry _ NY8T

I have to use the processor to achieve 80 watts out. Not sure if that is acceptable for measurements or not.

Rich McCabe

I shut the processor off because it drives the SSB scope wave form crazy and results with processor in general were not good.

The "bumps" are from the processor.

Larry _ NY8T

I just wired it up to the front mic jack and still get those bumps with any power level over about 2 or 3 watts and that is with the processor off and the mic gain below the 0 db on the level meter.

Rich McCabe

I just wired up the 8 pin and have to shut my mic gain down to zero or 1 or running my mic levels into the red.  So I assume it needs attenuation.

Larry, what does that like when you run full power? Is it worse?

Rich McCabe

Never mind. Just saw your second picture.  Thats no processor?

Larry _ NY8T

No processor, the ripples grow with output power.



Rich McCabe

I have it connected to 7 and 8 foster connector now.  But it works better on the balanced input.

I think it might be better when I get my 6600 as it should have two balanced inputs on the back.

I dont know what to think of the ripples. I would ask Larry what he thinks. 

Rich McCabe

Larry,  Just noticed I have more bumps with it on the foster connection even with processor off.

Larry _ NY8T

They get worse as the power rises.

KC2QMA_John

Looks like HUM in the audio, Try to connect the shield of the 1/8” cable coming from the LP500 and tie Pin's  5 & 6 together at the foster on the radio. This should do the trick.

Rich McCabe

Pins 5&6 or 5&7?

KC2QMA_John

OOPS Yes 5 & 7

KC2QMA_John

Pins 5 & 7!  NOT 5&6

Rich McCabe

No change when connecting pins 5 and 7.

This is from Larry at Telepost.

-10 dBV is 894mV p-p. The output of LP-500 is 350 to 500 mV p-p into a 10K load depending on the test signal, which is roughly 6 dB lower. I would think the input would have a range of plus and minus something relative to -10 dBV, but maybe it's just an attenuator on the input with no gain at all.

I thought my balanced line input looked cleaner but maybe not.

KY6LA_Howard

@Rich. You got me intrigued. I have. LP700 so I will try the same experiment when I return to the USA next week Question: looks like u have a power supply hum. Are you feeding both the LP500 and Flex from D.C. Or a linear supply rather than a switching supply?

KC2QMA_John

****! I was almost certain that would work.
I don't have A LP-500 yet but it on my wish list. 

Rich McCabe

Howard, everything in my shack is fed with my Astron 50 amp supply.

Not saying my setup is perfect but have tried to follow your quiet station guide.

Larry _ NY8T

I run an astron 70 linear supply and get the same results. Tonight i will supply the LP-700 with a battery and see what happens.

KC2QMA_John

Just a dumb question are you using a shielded audio cable for the 2 tone output?

Rich McCabe

Well I am.

KC2QMA_John

Like i said a dumb question

Rich McCabe

Never a dumb question. I have been known to overlook the obvious

Larry _ NY8T

I ran my LP-700 off a battery, no improvement with the ripple wave form.

KY6LA_Howard

Install soome ferrites on all the cables.

Rich McCabe

I have ferrites on everything. Most cables have at least two if not three depending on length. This includes power, USB and coax.

KY6LA_Howard

I will be back in the United States next week. I will put on my l system then