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Haven't powered up in a while. So I thought I would..? Measured the signal strength using a Calibrated HP Signal Generator..? at -73DBM.? OR S9..
I got the following..
??????????????????? R4C??????????? T4XC
3.5 ?? Mhz??????? S6????????????????? S2
7.1??? Mhz??????? S8????????????????? S9
14? ?? Mhz??????? S9????????????????? +10
21???? Mhz??????? +10??????????????? +10
28.5? Mhz???????? S9???????????????? +10
They should all be the same I would think...They are NOT
Question? Why??
Does this need a good alignment?? Looks like the 3.5 Mhz is way off..
Skip
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The R-4C is not S9 with a -73 dBm test signal.? -80 dBm to even -85 dBm is more typical for S9 from 80m through 10m.?? 160m is typically 10 dB lower in gain.?
(That doesn’t matter at all due to 160m band noise.)
?
If in transceive mode, the T-4XC LO injection is another variable as your data appears to show.? None of the Drake mixers are near saturation, thus gain differences
are typical in transceive mode due to LO level differences.?
?
As a starting point consider the attached alignment tips.? (You can ignore the FPS-4 information.)
?
Rob, NC0B
?
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From: [email protected] [mailto:[email protected]]
On Behalf Of Skip via groups.io
Sent: Monday, March 27, 2023 2:51 PM
To: [email protected]
Subject: [DRAKE-RADIO] Drake T4XC and R4C
?
Haven't powered up in a while. So I thought I would..? Measured the signal strength using a Calibrated HP Signal Generator..? at -73DBM.? OR S9..
I got the following..
??????????????????? R4C??????????? T4XC
3.5 ?? Mhz??????? S6????????????????? S2
7.1??? Mhz??????? S8????????????????? S9
14? ?? Mhz??????? S9????????????????? +10
21???? Mhz??????? +10??????????????? +10
28.5? Mhz???????? S9???????????????? +10
They should all be the same I would think...They are NOT
Question? Why??
Does this need a good alignment?? Looks like the 3.5 Mhz is way off..
Skip
|
People would be better off if they scraped the numbers off the old rigs s-meters.
As you have a calibrated generator you probably have a meter you can put across the speaker.? Send in a low level signal in the two rigs and see if you can hear or measure the audio at the speaker and see if the two? rigs seem to hear the weak signal equally.? This will tell you if the low s-meter indicates a problem or just a low meter reading.
Ralph ku4pt
On Monday, March 27, 2023 at 04:51:31 PM EDT, Skip via groups.io <wb4yvo@...> wrote:
Haven't powered up in a while. So I thought I would..? Measured the signal strength using a Calibrated HP Signal Generator..? at -73DBM.? OR S9.. I got the following.. ??????????????????? R4C??????????? T4XC 3.5 ?? Mhz??????? S6????????????????? S2 7.1??? Mhz??????? S8????????????????? S9 14? ?? Mhz??????? S9????????????????? +10 21???? Mhz??????? +10??????????????? +10 28.5? Mhz???????? S9???????????????? +10 They should all be the same I would think...They are NOT Question? Why?? Does this need a good alignment?? Looks like the 3.5 Mhz is way off.. Skip
_._,_._,_
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Hi Ralph,
?
This isn’t two rigs, but one receiver and one transmitter that can be operated as separates or transceive off of either VFO.
?
With this much gain discrepancy between 80m and 15 meters there is a problem, likely alignment.? There could be some variation in the different band crystal
output level, but I doubt it.? For certain the AGC threshold is all over the map.? A 1 microvolt signal (-107 dBm) should read S3 on all bands 80 – 10 meters.? With those S meter readings there is no chance the S meter will read S3 at -107 dBm on all bands.
?
With low gain on 80 and 40m reception may not be drastically affected since band noise is so much higher on the low bands.? The bottom line is Skip asked if
this was the way the R-4C should operate and it is not operating anywhere near spec.
?
Rob, NC0B
?
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Show quoted text
From: [email protected] [mailto:[email protected]]
On Behalf Of Ralph Mowery via groups.io
Sent: Monday, March 27, 2023 4:15 PM
To: [email protected]; [email protected]
Subject: Re: [DRAKE-RADIO] Drake T4XC and R4C
?
People would be better off if they scraped the numbers off the old rigs s-meters.
As you have a calibrated generator you probably have a meter you can put across the speaker.? Send in a low level signal in the two rigs and see if you can hear or measure the audio at
the speaker and see if the two? rigs seem to hear the weak signal equally.? This will tell you if the low s-meter indicates a problem or just a low meter reading.
On Monday, March 27, 2023 at 04:51:31 PM EDT, Skip via groups.io <wb4yvo@...> wrote:
Haven't powered up in a while. So I thought I would..? Measured the signal strength using a Calibrated HP Signal Generator..? at -73DBM.? OR S9..
I got the following..
??????????????????? R4C??????????? T4XC
3.5 ?? Mhz??????? S6????????????????? S2
7.1??? Mhz??????? S8????????????????? S9
14? ?? Mhz??????? S9????????????????? +10
21???? Mhz??????? +10??????????????? +10
28.5? Mhz???????? S9???????????????? +10
They should all be the same I would think...They are NOT
Question? Why??
Does this need a good alignment?? Looks like the 3.5 Mhz is way off..
Skip
|
Rob:
Would the procedures set forth in that document also be applicable to a R4b / T4xc combo?
Tnc es 73 de Arnie W8DU
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Arnie,
I have used this method for quite some time, with all lines, and it is definitely? LOT less hassle than swamping the premixer.? The tuned band circuits are pretty much identical across the versions (A,B,C).
Another thing to be aware of is that when aligning the transmitter, the caps are adjusted with no receiver or cables connected.? The INJ cable was designed with a specific capacitance so that it should match when connected together.? Some trouble comes when a substitute cable is used because it throws off the tuning.? If you have a different INJ cable (using coax or a different length), then the transmitter and receiver will need to be aligned when they're connected.
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
------- Original Message -------
On Tuesday, March 28th, 2023 at 9:24 AM, W8DU_Arnie <mdjdmi@...> wrote:
Rob:
Would the procedures set forth in that document also be applicable to a R4b / T4xc combo?
Tnc es 73 de Arnie W8DU
|
Arnie,
The front end alignment portion would apply to any of the R-4 line. ?
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On Mar 28, 2023, at 7:24 AM, W8DU_Arnie <mdjdmi@...> wrote:
?Rob:
Would the procedures set forth in that document also be applicable to a R4b / T4xc combo?
Tnc es 73 de Arnie W8DU
|
Hi Steve,
I have a pretty old, but original inj cable. Do the characteristics change over time? I have been aligning without the connections.
thanks,
gregg
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Gregg,
If you are going to use with the T4XC, align it with it connected to the transmitter. The injection and antenna cables need to be drake spec cables. That does make a big difference overall. My R4C hears better than my Icom 7300...significantly for in the mud DX. MY R4C is the go getter for weak signal work after being fully aligned.
On Tuesday, March 28, 2023 at 12:06:44 PM EDT, Gregg Lebovitz <gregglebovitz@...> wrote:
Hi Steve,
I have a pretty old, but original inj cable. Do the characteristics change over time? I have been aligning without the connections.
thanks,
gregg
|
The procedures in the manuals call for each to be aligned without being connected to the other.? That is the basic alignment and, with the correct INJ cable, should work equally from the TX or RX as the frequency control.? If there are discrepancies, I would look at the cable first.? The cable material and length were chosen so that the TX and RX keep their alignment when connected together, so if you've done the alignment on both the TX and RX and the TX is giving you less sensitivity, that could indicate a bad cable.
The cables were chosen for a value of capacitance and not for impedance.? Only the INJ cable on the B and earlier sets has this spec.? All other cables can be basic audio-quality cables -- including the RX ANT.? On the C Line, the CAR OSC cable is also made for RF but I'm not certain what its spec was or is.? I've used quality coax for that cable, as the appearance of the factory cables appears to be the same as the INJ cable.
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
------- Original Message -------
On Tuesday, March 28th, 2023 at 12:06 PM, Gregg Lebovitz <gregglebovitz@...> wrote:
Hi Steve,
I have a pretty old, but original inj cable. Do the characteristics change over time? I have been aligning without the connections.
thanks,
gregg
|
Just measured my cables? They are anywhere from 90 pf? to 271 pf? most are around 100-115 pf.? My question is for the inj and car osc cable what is the capacitance in a 3 foot run.. all my cables are about 3 foot take a few inches..
I guess you use RG-62 cable..? but I do not think any of mine are that..? At lease its not marked.
Skip
|
Those are all high-capacitance.? You should have 60 pF, total.
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
------- Original Message -------
On Thursday, March 30th, 2023 at 1:33 PM, Skip via groups.io <wb4yvo@...> wrote:
Just measured my cables? They are anywhere from 90 pf? to 271 pf? most are around 100-115 pf.? My question is for the inj and car osc cable what is the capacitance in a 3 foot run.. all my cables are about 3 foot take a few inches..
I guess you use RG-62 cable..? but I do not think any of mine are that..? At lease its not marked.
Skip
|
The definitive word on Drake interface cables:
To quote K4OAH - still with us in many ways....
All original cables were 38" long tip-to-tip.
The INJ, (and CAR OSC in the C-Line,) cables used a foam inner dielectric and
phono connectors
with a white insulation. This cable measures 60 pF total capacity.
All other cables used the standard for the day clear polyethelene inner
dielectric and phenolic
(brown) insulated phono connectors and measure ~100 pF.
Original Drake INJ & CAR OSC Cables ?? 19
pF/ft?????????? 0.160" o.d. (foam
poly)
RG-62 ??????????? ??????????????????????? 93R???????????????? 13.5
pF/ft??????? 0.240" o.d.
RG-59???????????? ?????????????????????? 75R???????????????? 14.8
pF/ft??????? 0.242" o.d.
RG-6 ????????????????????????????????????? 75R???????????????? 16.2 pF/ft??????? 0.270" o.d.
RG-174????????????????????????????????? 50R???????????????? 30.8 pF/ft??????? 0.110" o.d.
Mic Cable (Belden 8410)???? Hi-Z???????????????? 33 pf/ft??????????? 0.160" o.d. (foam poly)
Mic Cable (Belden 8421)???? Hi-Z???????????????? 16 pf/ft??????????? 0.180" o.d. (foam poly)
R/S Audio Patch Cable??????????????????????????????? 28
pF/ft?????????? 0.165" o.d. (poly)
The best choice is the Belden 8421 Audio cable from their
"Brilliance" line. It looks just like
the other cables, and is very flexible. K0UYA, another list member, had some
8421 at one time
that he was selling by the foot. The RG-62 is OK, but it is 50% larger and far
less flexible.
RG-62 is also prone to shorting if bent over too small a radius, and is
susceptible to heat
damage when soldering connectors. The best "feature" of RG-62 is that
it is often FREE, since
there have been many miles of it pulled out of old computer networks.
The only pertinent factor is the total capacity. Impedance and "loss"
are not important.
Any _reasonably low capacity_ coax will work if the units are cabled together
for the
adjustment of the INJ trimmers.
The cable type ONLY affects the LEVEL of the PreMix signal, (5.645 MHz ABOVE
the
transmit/receive frequency,) and a small DC control voltage between the two. If
the shunt
capacity is too high, insufficient LO level for the first mixer will reduce the
sensitivity of
the receiver and the output power of the transmitter.
Some of the "commercial" cable mfrs use RG-59A, but it's a little larger
and also prone to
shorting if bent over too tight a radius.
The ANT lead to the receiver is too short to matter, but you want good shield
integrity, which
usually eliminates R/S cables.
The best connectors I've found are the Switchcraft 3502 plugs, available from
just about anyone,
Digikey, Mouser, Allied, Newark and just about any reputable parts place.
6-32 bolts thread into the same holes as the feet for the AC-4.
73, Garey - K4OAH
Rome, GA
Regards, - Steve? W7SJT "Always look for a positive solution then Improvise, Adapt, and Overcome" - Adaptation of the U.S. Marine Corps motto
"There are no rules here!...We're trying to accomplish something!!"
- Thomas Edison
"Success is not final, failure is not fatal.? It is the courage to continue that counts." -?Winston Churchill
?
On Thursday, March 30, 2023 at 11:33:25 AM MDT, Skip via groups.io <wb4yvo@...> wrote:
Just measured my cables? They are anywhere from 90 pf? to 271 pf? most are around 100-115 pf.? My question is for the inj and car osc cable what is the capacitance in a 3 foot run.. all my cables are about 3 foot take a few inches..
I guess you use RG-62 cable..? but I do not think any of mine are that..? At lease its not marked.
Skip
|
Skip
Rob Sherwood