FTV1000
RX SENSITIVITY TESTS by K1SIX revised 05 Feb 2003
Serious
6M Dxers often rely on out of band indicators to give them a "feel" for
conditions that may soon give them an early warning that 50 Mhz
propagation
may be favorable for them.
This
series of tests was conducted on the FTV1000 Transverter with all the
"bias"
expected from an avid 6M Dxer that has been using propagation
"indicators"
to full advantage for many years.
These tests are OBJECTIVE but DO NOT comply with the standard
method
of MDS measurements with a characterised square law detector! The tests
utilize Joe Taylor's (K1JT) WSJT "MEASUREMENT MODE" and an RF Signal
Generator
with calibrated attenuator to estimate MDS. The tests should be
reproducable
by others for comparison purposes provided the WSJT Measure Mode is
tested
for calibration. My calibration tests reveal that when a weak signal
(-124
dBm) is set to exactly 0 dB in the Measure Mode and dropped exactly 3
dB
(-127 dBm), the WSJT Measure Mode also drops 3 dB to a new reading of
-3
dB. Therefore, in these tests the non-signal noise is set for a WSJT
Measure
Mode reading of -3 dB and the RF level recorded that produces a WSJT
Measure
Mode reading of exactly 0 dB. The WSJT application requires a
sound
card and may be
downloaded
for free via the Internet.These
are the conditions under which these MDS were conducted:
1-CW
Mode, dual 500 Hz Filters in the IFs of the FT1000MP Mark V
2-Mark
V IPO ON, AGC OFF, Transverter receive to Mark V RX IN jack
3-CW
Mode, AGC OFF, 500Hz single IF Filter for the existing R9000 system
4-3'
1/4" Superflex jumper to signal generator.
5-WSJT
0 dB reading to determine MDS (see diagram for sig. gen. injection
point)
Here's
the results (settings refer to FTV1000 settings):
ORIGINAL BENCH TESTS WITH ARR PA45VDG on
R9000
|
FREQUENCY
|
FTV1000 IPO ON
|
FTV1000 Preamp #1
|
FTV1000 Preamp #2
|
R9000 with MULTICOUPLER
|
|
50.110 *
|
-129.1 dBm
|
-135.8 dBm
|
-139.1 dBm
|
-146.8 dBm
|
|
49.750 *
|
-128.4 dBm
|
-137.4 dBm
|
-140.0 dBm
|
-146.6 dBm
|
|
48.250 *
|
-124.2 dBm
|
-133.2 dBm
|
-139.9 dBm
|
-146.6 dBm
|
|
46.172 *
|
-115.0 dBm
|
-128.1 dBm
|
-135.6 dBm
|
-147.6 dBm
|
|
45.250 *
|
-112.3 dBm
|
-125.2 dBm
|
-134.6 dBm
|
-147.6 dBm
|
CONCLUSIONS
(based upon 50.110 baseline):
- Little
difference in loss as low as the 48.250 video indicator band
- Adequate
sensitivity at 48.250 to show indication WELL PRIOR to 6M opening
- Average
3.5 dB loss at 46.172 (Still adequate)
- Average
4.5 dB loss at 45.250 (Still adequate)
- Bench
tests are great but do NOT account for external noise contribution when
antenna is connected!
- External
noise contribution is a FACT OF LIFE on 6 meters and below. There
will always be some degradation from external sources whether they are
cosmic or manmade
- The
external
noise contribution will be HIGHER at lower frequencies
- BUT
the
external noise pickup from a high Q 50 Mhz antenna will be LESS at the
lower frequencies because it is not optimized there!!
- The
above
tests indicate a very capable receive system at lower "indicator"
frequencies
for the FTV1000.
Although
the FTV1000 provides adequate sensitivity on video carrier frequencies
to warn the 6M Op that an in-band opening is about to occur, I
find
it lacking the extreme out of band sensitivity required for maximum
advance
notice. To compensate, I use a second receiver and a multiple
receiver
distribution system. The newly constructed "K1SIX Magic Box" was
completed
and first air tested on 17 January 2003 and includes all the bells and
whistles required at this particular station. This actually adds
a "new" selectable front end to the FTV1000 depending upon the position
of the THRU switch, S2. When S2 is in the THRU position, a red
LED
illuminates as a warning. Therefore, by utilizing the
"Magic
Box", the following front end combinations are possible:
1-
THRU Switch= Normal, FTV1000 in IPO ON position: Provides GAASFET front
end optimized near 45 MHz and up to four receiver multicoupling.
2-
THRU Switch to THRU position: The FTV front end selections of IPO ON,
Preamp#1
and Preamp#2 operate as normal (the input to the 4 receiver
multicoupling
system is disconnected).
NOTE: An ARB-702Y is used to interface the
PTT (pin 2) and LINEAR (pin 8) FTV1000 signals. This buffer is
connected
to the LIN BAND DATA connector on the rear of the FTV1000. In
order
to prevent HOT SWITCHING of the T/R relay, a 10k pullup resistor
to 13 VDC must be added to the HANDSHAKING jack inside the ARB-702 and
the HANDSHAKING connection must be connected to either Sequencer
section
C or D. Thus, when the sequencer relay is open a current source through
the 10k pullup resistor will INHIBIT RF TRANSMISSION until such time as
the sequencer C or D relay grounds. This delayed ground will then
enable RF transmission.
Click
Here for a schematic of the "Magic Box"
The tables below show comparative sensitivity tests of the new
receiver
distribution system and two ARR preamps. These tests were
accomplished
in an identical manner as those described earlier. Note that all tests
utilized FTV1000 preamp #2 which will always show the best sensitivity
on the bench but using this front end is a poor choice in series with
the
outboard GAASFET preamp and an antenna connected due to the excessive
gain.
With the outboard preamp inline, the most sensitive practical choice is
shown in (brackets) consistent with the lowest possible gain. For
example, at 50.110 MHz a choice of IPO ON results is only a 2.3
dB
sensitivity reduction versus Preamp #2 while Preamp #1 shows only a .5
dB sensitivity reduction versus Preamp #2. The new system now
offers
many front end gain/NF choices including using only the FTV1000 mixer
as
a front end and with these choices the overall sensitivity across all
regions
of interest can be greatly improved- IF NEEDED.
OBJECTIVE TESTS WITH ARR PA45VDG PREAMP
|
FREQUENCY
|
FTV1000 PREAMP #2 THRU MODE
|
FTV1000 (Preamp #2) + Multicoupler
|
R9000 with Multicoupler
|
|
50.110 *
|
-139.1 dBm
|
-146.8 dBm (Preamp #1)
|
-146.8 dBm
|
|
49.750 *
|
-140.0 dBm
|
-147.9 dBm Preamp # 2)
|
-146.6 dBm
|
|
48.250 *
|
-139.9 dBm
|
-147.8 dBm (Preamp # 1)
|
-146.6 dBm
|
|
46.172 *
|
-135.6 dBm
|
-145.8 dBm (Preamp # 2)
|
-147.6 dBm
|
|
45.250 *
|
-134.6 dBm
|
-145.8 dBm (Preamp # 2)
|
-147.6 dBm
|
OBJECTIVE TESTS WITH ARR PA50VDG PREAMP
|
FREQUENCY
|
FTV1000 PREAMP #2 THRU MODE
|
FTV1000 (Preamp #2) + Multicoupler
|
R9000 with Multicoupler
|
|
50.110 *
|
-139.1 dBm
|
-145.8 dBm (Preamp # 1)
|
-146.0 dBm
|
|
49.750 *
|
-140.0 dBm
|
-148.0 dBm (Preamp # 2)
|
-146.7 dBm
|
|
48.250 *
|
-139.9 dBm
|
-147.0 dBm (Preamp # 1)
|
-143.8 dBm
|
|
46.172 *
|
-135.6 dBm
|
-141.4 dBm (Preamp # 2)
|
-144.6 dBm
|
|
45.250 *
|
-134.6 dBm
|
-145.8 dBm (Preamp # 2)
|
-147.6 dBm
|
- Note: 50.110
is the 6M DX calling frequency, 49.750 is the center of the East
Europe/
Asian TV video carrier band, 48.250 is the center of the West Europe
video
carrier band, 46.172
is the high ERP video carrier frequency for Australia (46.240 is also a
good VK indicator) and 45.250 is the center of the New Zealand video
carrier
frequency band. Most video carrier frequency bands are only 20 kHz wide
with a center (0) offset, a minus 10 kHz and a plus 10 kHz offset for
video
carriers which are AM and for all practical purposes (with a narrowband
IF filter choice)- a pure CW note.
Some
notes on NOISE BLANKER settings (for 6m):
Living
in a rural area,I am plagued by
power line noise problems.From this
hilltop I am LOS to many noisy insulators.Each
direction exhibits a different noise characteristic.For
me,the Mark V settings of A14, B13
and B15 work best and must be customized for each direction.Unfortunately,IF
Noise Blankers will exhibit overload from strong signals so keep the
gain
setting to as minimal as possible and if you can operate with the NB
off-
then do so!A 20 over S9 "local"
wipes out +/- 15 kHz here with his continuous CQs when I have the
blanker
ON and set for A14 (My NE optimized setting).USE
S-METER LITE freeware to determine best noise reduction setting in a
wide
ssb bandwidth.Adjust the gain to
MINIMUM required to do the job!Use
FAST and NB button combined to make quick adjustments.In
this programming mode,as you change
settings and/or turn the blanker on/off: S-METER LITE and the Mark V
will
remain ACTIVE so you can see the dynamic results of your settings!Once
happy- simply hit the ENT button to store the setting.It
is likely that POWER LINE noise characteristics will change with
temperature
and humidity so be prepared to reprogram your settings "on the fly" by
familiarization with the procedure.GL
with IF Blanking as it is a battle against physical limitations.In
order for a blanker to be effective,it's
"detection bandwidth" must be relatively wide so that the blanking
pulses
are not distorted by the stretching that would occur with narrow
detection
bandwidths.This is an inherent problem
with IF BLANKING.I'll bet that the
most effective blankers are the worst when it comes to adjacent channel
overload.This is The Nature of This
Beast.
I
hope some find these data of use 73 de K1SIX
