Low sensitivity and low noise floor

vu2mb
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Joined: Thu Nov 21, 2019 5:30 pm

Low sensitivity and low noise floor

Postby vu2mb » Mon Jul 27, 2020 2:56 pm

Hi Friends,

I have recently noticed that my 8000DLE is behaving in a weird way. Its noise floor suddenly goes down to -135 db from -105 and S meter on the same signal to -101 dbm (S4) from -67 dbm (S9+5). It was intermittent few times but today it remained on the bottom. What could be wrong and how to rectify it? Any help would be highly appreciated. I have reset the firmware. I am putting 2 screenshots of the same time with same signal. One is from 8000DLE and another one is from 200D.

200D shows signal at -67 dbm and 8000DLE at -101.

73

Bhanu
VU2MB
Attachments
ANAN 8000DLE noise floor and S meter.JPG
ANAN 8000DLE noise floor and S meter.JPG (164.5 KiB) Viewed 443 times
ANAN 200D noise floor and S meter.JPG
ANAN 200D noise floor and S meter.JPG (157.86 KiB) Viewed 443 times
vu2mb
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Re: Low sensitivity and low noise floor

Postby vu2mb » Mon Jul 27, 2020 3:31 pm

Additional points to my last post.

It may be something to do with resettable fuse?
As I was using FT8 and temp was around 48.
It seems not resetting now.
What's the safe temp limit?

73
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w-u-2-o
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Re: Low sensitivity and low noise floor

Postby w-u-2-o » Mon Jul 27, 2020 4:54 pm

I've been scratching my head all morning on this, but it seems you have a good answer now. Unfortunately I can't tell you what the safe temperature limit is. It looks like you are going to find out for us! :)

My 8000 runs in air conditioning and never over 40W, so it's never really been hot.
vu2mb
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Re: Low sensitivity and low noise floor

Postby vu2mb » Mon Jul 27, 2020 5:41 pm

Dear Scott
Can you please guide me where is this fuse in the radio?
It seems it is defunct or stuck.

I don't have the circuit diagram and it was you who pointed out that resettable fuse may be an issue when a similar issue was cropped up during winters. My radio too runs in ac but temperature shoots up when power is above 60 70W.

Currently I am using a dipole and needs more power when a weak ATNO or New on band comes up or running 40/80.
Would appreciate if you send me a copy of circuit diagram on my email mbsingh@gmail.com

Thank you,

73
Bhanu
VU2MB
kc2rgw
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Re: Low sensitivity and low noise floor

Postby kc2rgw » Mon Jul 27, 2020 6:03 pm

Just a generic comment. Digital modes even with the on/off cycle of FT8, are high duty cycle. It's much like AM or FM while transmitting.

I don't run any of my 100W rigs above 25W on digital modes. I know people out there say to give it hell on FT8, but I disagree after many years of running keyboard digital modes, PSK, Thor, Olivia, HF and VHF packet, JS8Call etc. The rigs just get too hot for my comfort. Keeping power at 25W or less, I've never cooked a rig and I am a loooong winded rag chewer with overs measured in minutes at a time easily on slower modes.

I offload and use an amplifier if I run digi modes at higher power (with the bands lately, this is often) to keep everything running cool.
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w-u-2-o
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Re: Low sensitivity and low noise floor

Postby w-u-2-o » Mon Jul 27, 2020 6:08 pm

vu2mb wrote:Dear Scott
Can you please guide me where is this fuse in the radio?
It seems it is defunct or stuck.

I don't have the circuit diagram and it was you who pointed out that resettable fuse may be an issue when a similar issue was cropped up during winters. My radio too runs in ac but temperature shoots up when power is above 60 70W.
Unfortunately Apache has requested that the schematics for the 7000 and 8000 series hardware not be publicly posted. You will need to email Apache and request those schematics, which they should send to you.

There is more than one PTC (positive temperature coefficient) device (aka "re-settable fuse") in the unit. They are labeled "F1, F2", etc. on the schematics. You will have to check each one if that's what you think the problem is.

Is your fan running OK? Is the fan vent not blocked?
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w-u-2-o
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Re: Low sensitivity and low noise floor

Postby w-u-2-o » Mon Jul 27, 2020 6:09 pm

w-u-2-o wrote:
vu2mb wrote:Dear Scott
Can you please guide me where is this fuse in the radio?
It seems it is defunct or stuck.

I don't have the circuit diagram and it was you who pointed out that resettable fuse may be an issue when a similar issue was cropped up during winters. My radio too runs in ac but temperature shoots up when power is above 60 70W.
Unfortunately Apache has requested that the schematics for the 7000 and 8000 series hardware not be publicly posted. You will need to email Apache and request those schematics, which they should send to you.

There is more than one PTC (positive temperature coefficient) device (aka "re-settable fuse") in the unit. They are labeled "F1","F2", etc. on the schematics. You will have to check each one if that's what you think the problem is.

Is your fan running OK? Is the fan vent not blocked?
vu2mb
Posts: 31
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Re: Low sensitivity and low noise floor

Postby vu2mb » Mon Jul 27, 2020 6:48 pm

Dear Scott,

Yes the fan is running. Are these PTC's on main Trx board?

73
Bhanu
vu2mb
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Re: Low sensitivity and low noise floor

Postby vu2mb » Mon Jul 27, 2020 6:50 pm

kc2rgw wrote:Just a generic comment. Digital modes even with the on/off cycle of FT8, are high duty cycle. It's much like AM or FM while transmitting.

I don't run any of my 100W rigs above 25W on digital modes. I know people out there say to give it hell on FT8, but I disagree after many years of running keyboard digital modes, PSK, Thor, Olivia, HF and VHF packet, JS8Call etc. The rigs just get too hot for my comfort. Keeping power at 25W or less, I've never cooked a rig and I am a loooong winded rag chewer with overs measured in minutes at a time easily on slower modes.

I offload and use an amplifier if I run digi modes at higher power (with the bands lately, this is often) to keep everything running cool.


I agree with your views.
73
Bhanu
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w-u-2-o
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Re: Low sensitivity and low noise floor

Postby w-u-2-o » Mon Jul 27, 2020 6:52 pm

There are PTCs on the Orion MKII board, and I think there may be some on the RF amp board as well, but I'm not sure.
K9RX
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Re: Low sensitivity and low noise floor

Postby K9RX » Tue Jul 28, 2020 11:36 am

I'm confused why you went to suggesting a fuse on this? It looks to me like you have TERRIBLE noise at your location and it simply went away! -101 is a little bit high for me here with a 2.4Khz passband ... and -67 is terrible noise - but it appears like I'm seeing the same signal and not seeing the second signal on the 'high noise' picture ... possibly he was just gone or he is now buried in the noise.

Gary
K9RX
K1LSB
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Re: Low sensitivity and low noise floor

Postby K1LSB » Tue Jul 28, 2020 5:09 pm

Another possibility is that the prefilter is turned off and BCAM is overwhelming the receiver front end.
vu2mb
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Re: Low sensitivity and low noise floor

Postby vu2mb » Wed Jul 29, 2020 3:44 pm

There may be minor time difference of few seconds amongst both screenshots thats why one signal is weak.
Next day i opened the top cover to check the PTC's but before going ahead, I switched on the radio
to realize its just working fine. day before it was in a bad shape even after 12 hours of cooling off !!

Looks like there is some other issue like lose cable or something. Will find out at the next time.
Thank you very much friends to spare time and providing your valuable inputs.

Thinking of putting an extra fan to keep radio cooler.

73
Bhanu
VU2MB
vu2mb
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Re: Low sensitivity and low noise floor

Postby vu2mb » Thu Jul 30, 2020 10:20 am

kc2rgw wrote:Just a generic comment. Digital modes even with the on/off cycle of FT8, are high duty cycle. It's much like AM or FM while transmitting.

I don't run any of my 100W rigs above 25W on digital modes. I know people out there say to give it hell on FT8, but I disagree after many years of running keyboard digital modes, PSK, Thor, Olivia, HF and VHF packet, JS8Call etc. The rigs just get too hot for my comfort. Keeping power at 25W or less, I've never cooked a rig and I am a loooong winded rag chewer with overs measured in minutes at a time easily on slower modes.

I offload and use an amplifier if I run digi modes at higher power (with the bands lately, this is often) to keep everything running cool.


While I agree on everything what you said. Just to add that 8000DLE is a 200W radio and rated for 50W on AM and as per specifications its rates for 200W on SSB FM and Digital modes. 1:3 CCS will still result in shooting the temperature unless you are in a cold places like US and Europe. In Places like India 60-70W FT8 active dx will take temp towards 45-48 degrees in a 28 degree ambient room temperature in 15-20 minutes. One solution may be to add another fan to force cooling to this otherwise a war horse.

73
Bhanu
K9RX
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Re: Low sensitivity and low noise floor

Postby K9RX » Thu Jul 30, 2020 11:33 am

I never had an issue running the 8000 at 60 - 70W on FT8. Didn't get very warm at all.

But again: you've not addressed my comment - this looks to have no relationship with temperature - or am I missing something? It looks like you have a nearby noise source in one shot (the -67) and that noise source is off/gone in the other.

Gary
K9RX
vu2mb
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Re: Low sensitivity and low noise floor

Postby vu2mb » Thu Jul 30, 2020 2:51 pm

K9RX wrote:I never had an issue running the 8000 at 60 - 70W on FT8. Didn't get very warm at all.

But again: you've not addressed my comment - this looks to have no relationship with temperature - or am I missing something? It looks like you have a nearby noise source in one shot (the -67) and that noise source is off/gone in the other.

Gary
K9RX


Dear Gary,

Those 2 screen shots are from two different radios. First screenshot is of 8000DLE and second one is from 200D ( just 30 seconds apart) and that's why they have different noise floor levels. 8000DLE when gets hot, its PTC cut off some circuitry and sensitivity goes low. I am not technical so cant explain why? when its cools down it works normally. Second screen shot is from 200D which was okay and thats why it shows strong signal and higher noise floor.

You must be in a cool atmosphere and 8000's LCD may not be showing you 40+ temperature but here in India when outside temperature is around 32 I dont feel like using AC and fan works just fine and 8000DLE gets hot internally but not the outer case as Heat sink is not connected to it.

I have just come back from Seattle 12 days ago after a five months stay and got with me plenty of fair rite ferrites and snap on's to do whatever I can do to reduce or eliminate noise in the shack.

73
Bhanu
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w-u-2-o
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Re: Low sensitivity and low noise floor

Postby w-u-2-o » Thu Jul 30, 2020 4:57 pm

It could also be a bad solder connection on some component that opens up at hot.
greg
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Re: Low sensitivity and low noise floor

Postby greg » Fri Jul 31, 2020 4:39 pm

Had the same problem on my 8; found intermittent 4 pin molex connector to RF output board. Connector is to ant out pub.
Try wiggling it.

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