Tony Giacometti wrote in
news:VvSdnQC_g_Sb0qLanZ2dnUVZ_hKdnZ2d@hawaiiantel. net:

So, what to do, I followed the instructions for building the loop from
W2YR and KN4LF and from this link
http://www.hard-core-dx.com/nordicdx.../coaxloop.html

I think you are describing a scenario where, with the loop+preamp, the
receiver system is limited by internal noise rather than external noise.

So, it is a two band design, and that complicates matters somewhat.

Just concentrating on the 160m loop...

My calcs are that the 160m loop alone, tuned for zero series reactance
(should need ~90pF) and loaded with 50 ohms should have equivalent gain
of around -47dBi.

You would have to consider the preamp NF and gain and receiver NF to
evaluate the system noise floor, and you haven't given those details
(though they may be implied... but I am not familiar with the preamp you
are using).

Without using a preamp, the external noise (based on ITU-R P.372-8
Residiential man made noise) with this loop ought be of about the same
magnitude as the internal noise of a good transceiver, give or take. For
a preamp to improve the situation, it would need a NF significantly
better than the transceiver and sufficient gain to overcome the
transceiver noise.

Owen

Owen Duffy wrote:

Tony Giacometti wrote in
news:VvSdnQC_g_Sb0qLanZ2dnUVZ_hKdnZ2d@hawaiiantel. net:

So, what to do, I followed the instructions for building the loop from
W2YR and KN4LF and from this link
http://www.hard-core-dx.com/nordicdx.../coaxloop.html

I think you are describing a scenario where, with the loop+preamp, the
receiver system is limited by internal noise rather than external noise.

So, it is a two band design, and that complicates matters somewhat.

Just concentrating on the 160m loop...

My calcs are that the 160m loop alone, tuned for zero series reactance
(should need ~90pF) and loaded with 50 ohms should have equivalent gain
of around -47dBi.

You would have to consider the preamp NF and gain and receiver NF to
evaluate the system noise floor, and you haven't given those details
(though they may be implied... but I am not familiar with the preamp you
are using).

Without using a preamp, the external noise (based on ITU-R P.372-8
Residiential man made noise) with this loop ought be of about the same
magnitude as the internal noise of a good transceiver, give or take. For
a preamp to improve the situation, it would need a NF significantly
better than the transceiver and sufficient gain to overcome the
transceiver noise.

Owen

here are links to the preamps I use

http://www.iceradioproducts.com/reconly.html

http://www.isp.ca/ve3nh/kd9sv.htm

Tony Giacometti wrote in news:CpKdnabH6fWF-
:

here are links to the preamps I use

http://www.iceradioproducts.com/reconly.html

NF=1.8dB and Gain=18dB


http://www.isp.ca/ve3nh/kd9sv.htm

Ok, I can't work with specs like "Noise figure is quite low and the
design appears to have no vices." I am not saying it is bad, it just
doesn't say anything meaninful... well to me anyway.

Still no info on the transceiver, but lets guess it has a NF=8dB.

Transceiver + preamp has a NF of 2dB, which suggests an equivalent noise
floor of about -139dBm (2kHz bandwidth).... provided that the preamp
doesn't generate internal noise due to IMD and which would not be
captured in the 1.8dB spec NF.

ITU-R P.372-8 suggests ambient noise on 1.8MHz in Residential locality
should be about -75dBm+AvgAntGain or about -122dBm, so you should get
noticeably more noise (~17dB) from the loop than from a dummy load. That
would mean the configuration should deliver almost as good a S/N ratio as
possible... even though the S meter reading might be shy.

Again, I am talking about the 160m loop alone. You can't diagnose this
easily with the two loops in parallel.

Owen

Owen Duffy wrote:

Tony Giacometti wrote in news:CpKdnabH6fWF-
:

here are links to the preamps I use

http://www.iceradioproducts.com/reconly.html

NF=1.8dB and Gain=18dB


http://www.isp.ca/ve3nh/kd9sv.htm

Ok, I can't work with specs like "Noise figure is quite low and the
design appears to have no vices." I am not saying it is bad, it just
doesn't say anything meaninful... well to me anyway.

Still no info on the transceiver, but lets guess it has a NF=8dB.

Transceiver + preamp has a NF of 2dB, which suggests an equivalent noise
floor of about -139dBm (2kHz bandwidth).... provided that the preamp
doesn't generate internal noise due to IMD and which would not be
captured in the 1.8dB spec NF.

ITU-R P.372-8 suggests ambient noise on 1.8MHz in Residential locality
should be about -75dBm+AvgAntGain or about -122dBm, so you should get
noticeably more noise (~17dB) from the loop than from a dummy load. That
would mean the configuration should deliver almost as good a S/N ratio as
possible... even though the S meter reading might be shy.

Again, I am talking about the 160m loop alone. You can't diagnose this
easily with the two loops in parallel.

Owen


I am using a heavily modified Drake R-4c receiver. Sherwood mods.
And I at this point I only built the 80 meter loop as I wanted to make sure
it worked on 80 before I went and built one for 160.

I don't think ITU-R P.372-8 had my neighborhood in mind when it was
composed.

S-9 on this receiver is about the minimum on 160 and S-7 is the minimum on
75.

Much of the time its higher and a royal pain in the arse.

Tony Giacometti wrote in
news:bcSdnVU4bZ7W86LanZ2dnUVZ_vShnZ2d@hawaiiantel. net:


I am using a heavily modified Drake R-4c receiver. Sherwood mods.
And I at this point I only built the 80 meter loop as I wanted to make
sure it worked on 80 before I went and built one for 160.

I obviously misunderstood you when you provided a link to a two band
antenna... or did you forget to tell us that?

I will let you rework the calcs for your scenario.


I don't think ITU-R P.372-8 had my neighborhood in mind when it was
composed.

S-9 on this receiver is about the minimum on 160 and S-7 is the
minimum on 75.

S meter readings are pretty meaningless, but using the convention of 50uV
for S 9, 6dB/SPoint, ITU-R P.372-8 does indeed suggest median noise at
~S7 for a 2kHz bandwidth and Residential locale.

As to whether your receiver indicates S7 accurately, that is another
matter.

People who brag about S1 noise level on 80m have a lossy antenna and/or
(and) an innaccurate S meter.


Much of the time its higher and a royal pain in the arse.


Something many of us experience.

Owen

Owen Duffy wrote:

Tony Giacometti wrote in
news:bcSdnVU4bZ7W86LanZ2dnUVZ_vShnZ2d@hawaiiantel. net:


I am using a heavily modified Drake R-4c receiver. Sherwood mods.
And I at this point I only built the 80 meter loop as I wanted to make
sure it worked on 80 before I went and built one for 160.

I obviously misunderstood you when you provided a link to a two band
antenna... or did you forget to tell us that?

I used the design for the 80 meter loop - I would think they are mostly
independent of each other.



I will let you rework the calcs for your scenario.

????



I don't think ITU-R P.372-8 had my neighborhood in mind when it was
composed.

S-9 on this receiver is about the minimum on 160 and S-7 is the
minimum on 75.

S meter readings are pretty meaningless, but using the convention of 50uV
for S 9, 6dB/SPoint, ITU-R P.372-8 does indeed suggest median noise at
~S7 for a 2kHz bandwidth and Residential locale.

As to whether your receiver indicates S7 accurately, that is another
matter.

S-9 is 50 uv on this receiver on 40meters - can't be sure its exactly the
same on 80, but the calibration voltage for S9 is very very close on 80.




People who brag about S1 noise level on 80m have a lossy antenna and/or
(and) an innaccurate S meter.

or they are lying........



Much of the time its higher and a royal pain in the arse.


Something many of us experience.

Owen