Hello Gary,

You've posted some interesting information.

I wondered about the inherent non-linearities and, of course, the
deviation at which the SINADs were measured is not known, either. So the
question boils down to whether modern VHF receivers for marine use are
likely to have noticeably different sensitivity performance.

As you know, SINAD is a measure of "useful sensitivity" and the noise
plus distortion part of SINAD (rather than the signal part) is what is
probably affecting the differences in VHF receiver SINAD measurement.

Taking the issue into the realm of the real world, Icom quotes the
following for their IC-F4GT/GS radios:

0.3 microvolts for 12 dB SINAD
0.79 microvolts for 20 dB SINAD

The TK3160E UHF Transceiver reports similar results:

0.25 microvolts for 12 dB SINAD
0.63 microvolts for 20 dB SINAD

These both work out to Meindert's results very closely. So we know that
by assuming linearity, we are not necessarily wildly out of the ballpark.

I'm not sure how you derived the distortion percentages you mentioned,
but normally a receiver's distortion figure would be measured with an
input signal on the order of 0.5 to 1.0 volt to ensure that noise
doesn't affect the measurement. Under these conditions, a SINAD reading
of 12 dB corresponds to 25% distortion, while a reading of 20 dB
corresponds to 10% distortion.

73,

Chuck

"chuck" wrote in message
ink.net...
Hello Gary,

You've posted some interesting information.

I wondered about the inherent non-linearities and, of course, the
deviation at which the SINADs were measured is not known, either.

The SINAD is measured with a single tone and the measured audio output is
bandwidth limited with a filter with strict specifications, commonly known
as as CCITT or P53 filter.

So the
question boils down to whether modern VHF receivers for marine use are
likely to have noticeably different sensitivity performance.

As you know, SINAD is a measure of "useful sensitivity" and the noise
plus distortion part of SINAD (rather than the signal part) is what is
probably affecting the differences in VHF receiver SINAD measurement.

Taking the issue into the realm of the real world, Icom quotes the
following for their IC-F4GT/GS radios:

0.3 microvolts for 12 dB SINAD
0.79 microvolts for 20 dB SINAD

The TK3160E UHF Transceiver reports similar results:

0.25 microvolts for 12 dB SINAD
0.63 microvolts for 20 dB SINAD

These both work out to Meindert's results very closely. So we know that
by assuming linearity, we are not necessarily wildly out of the ballpark.

Indeed. 0.63 vs 0.uV is 8dB, as well as 0.25 vs 0.63 mV.

Meindert

Meindert Sprang wrote:

I wondered about the inherent non-linearities and, of course, the
deviation at which the SINADs were measured is not known, either.


The SINAD is measured with a single tone and the measured audio output is
bandwidth limited with a filter with strict specifications, commonly known
as as CCITT or P53 filter.



Hello Meindert,

My comment about deviation referred to the fact the the EIA standard
specifies that the signal generator deviation be at 60% of the peak
deviation used for that service (if I recall correctly). While it is
probably safe to assume that the peak deviation was the same for all
three receivers, there is no way of knowing whether SINAD was measured
using the specified 60% deviation.

Chuck

Lets hear nominees for the VHF rcvr hall of fame. Two votes I'd make are early
Motorola Modar, their 12 ch xtal controlled and the first full channel synth
(can't remmeber model no. something like 55/75) . These were hot rcvrs and had
GREAT intermod rejection, would work just fine in urban harbor environments
where pager xmtrs would clobber all other marine VHFs. One other vote is an
unsual combo, the Kenwood R 5000 rcvr with the factory VHF converter. Red hot
sensitivity and low noise. Could actually hear comms that were unintelligable
on other sets using the same antenna.

In article ,
(BOEING377) wrote:

Lets hear nominees for the VHF rcvr hall of fame. Two votes I'd make are early
Motorola Modar, their 12 ch xtal controlled and the first full channel synth
(can't remmeber model no. something like 55/75) . These were hot rcvrs and had
GREAT intermod rejection, would work just fine in urban harbor environments
where pager xmtrs would clobber all other marine VHFs. One other vote is an
unsual combo, the Kenwood R 5000 rcvr with the factory VHF converter. Red hot
sensitivity and low noise. Could actually hear comms that were unintelligable
on other sets using the same antenna.

I'll second that vote for the Modar's. We still have a pile of those
rigs kicking around the North Pacific fishing fleet, and they are
coveted as if they were Gold. Unfortunatly there are VERY few techs
that still work on those, and the spare parts are getting fewer all the
time. I have a 55/75 with dual receivers in my house as a Limited Coast
Base Station, and it has the .0002 tolerance mod for Coast Station use.
They are one of the best VHF's, ever made. The SEA156 comes in a close
Second, in my opinion, I have one of those as well.


Bruce in alaska
--
add a 2 before @

"Bruce in Alaska" wrote in message
...
In article ,
(BOEING377) wrote:

Lets hear nominees for the VHF rcvr hall of fame. Two votes I'd make are
early
Motorola Modar, their 12 ch xtal controlled and the first full channel
synth
(can't remmeber model no. something like 55/75) . These were hot rcvrs
and had
GREAT intermod rejection, would work just fine in urban harbor
environments
where pager xmtrs would clobber all other marine VHFs. One other vote is
an
unsual combo, the Kenwood R 5000 rcvr with the factory VHF converter.
Red hot
sensitivity and low noise. Could actually hear comms that were
unintelligable
on other sets using the same antenna.

I'll second that vote for the Modar's. We still have a pile of those
rigs kicking around the North Pacific fishing fleet, and they are
coveted as if they were Gold. Unfortunatly there are VERY few techs
that still work on those, and the spare parts are getting fewer all the
time. I have a 55/75 with dual receivers in my house as a Limited Coast
Base Station, and it has the .0002 tolerance mod for Coast Station use.
They are one of the best VHF's, ever made. The SEA156 comes in a close
Second, in my opinion, I have one of those as well.


Bruce in alaska
--
add a 2 before @

The Modars are getting difficult to find parts for and even the SEA 156s
have some parts shortages now such as replacement keypads. The new
replacement microphones are not holding up in commercial very well either.
Any of these units considered non-repairable do not end up in the discard
pile. They are reverently placed on the parts to be cannibalized shelf. eBay
searches have found a few SEA156 replacements and we are selling the SEA157
as a replacement, but teaching old skippers to use the 157 remains a
problem. They love those old 156s.
73 Doug K7ABX

"chuck" wrote in message
ink.net...
Meindert Sprang wrote:

I wondered about the inherent non-linearities and, of course, the
deviation at which the SINADs were measured is not known, either.


The SINAD is measured with a single tone and the measured audio output
is
bandwidth limited with a filter with strict specifications, commonly
known
as as CCITT or P53 filter.



Hello Meindert,

My comment about deviation referred to the fact the the EIA standard
specifies that the signal generator deviation be at 60% of the peak
deviation used for that service (if I recall correctly).

The ETSI specifies a deviation of 12.5% of the channel spacing. I don't know
what the EIA standard specifies.
But indeed, one has to assume they were all measured using the same
deviation.

Meindert