I'm confused about being illegal to transmit on the CB band.
"The Citizens Band (CB) Service is licensed by rule. This means an individual license is not required to operate a CB device. You can operate a CB device regardless of your age and for personal or business use so long as you are not a representative of a foreign government."
Larry
On Sun, Mar 30, 2014 at 9:25 PM, Shirley M¨¢rquez D¨²lcey <mark@...> wrote:
?
It should work with an Ensemble built for 15/12/10m operation. It would be illegal to transmit on that band in the US. (Receiving is legal.) I don't know what the relevant laws are in Brazil but I suspect it would also be illegal there.
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Hello,? Here in Brazil i think it?s illegal transmit with homemade equipaments.
My doubts are about HDSDR, cause some softwares, like PSDR, inhibit automaticaly some frequencies. Only for information.
Many thanks and 73.
---In softrock40@..., <mark@...> wrote : It should work with an Ensemble built for 15/12/10m operation. It would be illegal to transmit on that band in the US. (Receiving is legal.) I don't know what the relevant laws are in Brazil but I suspect it would also be illegal there.
On Sun, Mar 30, 2014 at 9:55 PM, <marcosbazzo@...> wrote:
?Hey, there.
It?s possible to transmit in CB band (26.65 to 27.99MHz) with Ensemble RXTX and HDSDR?
73.
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It should work with an Ensemble built for 15/12/10m operation. It would be illegal to transmit on that band in the US. (Receiving is legal.) I don't know what the relevant laws are in Brazil but I suspect it would also be illegal there.
On Sun, Mar 30, 2014 at 9:55 PM, <marcosbazzo@...> wrote:
?
Hey, there.
It?s possible to transmit in CB band (26.65 to 27.99MHz) with Ensemble RXTX and HDSDR?
73.
|
Hey, there.
It?s possible to transmit in CB band (26.65 to 27.99MHz) with Ensemble RXTX and HDSDR?
73.
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Roger
Haha.... I am glad I have never made a measurement mistake and then posted the results on this board ... NOT! Good catch on the MFJ level. Yours in much heftier than mine.
Half a volt P-P is not going to hurt the RXII but it will very likely drive the op amps into overload. Or if it doesn't then you have found a problem. You can use this level and check with a scope that it is delivered without much attenuation all the way to the mixer input pins. With this you can easily validate the performance of the receiver itself. But any use of the HDSDR readings and signals when the input is that high will not be useful because the op amps will be going rail to rail and making square waves and all kinds of messy nonsense that shows up a spurious signals on the display.
In order to not drive the op amps into overload you need to get the input below about 60 mV P-P which would be -20 dBm with a 50 ohm load. This is still high enough to trace with a scope and it will not crash into any low bridges in the op amps or sound card.
Good luck
Warren Allgyer
9V1TD
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Hi Mike
This has turned into a very long thread and you may not have read some of the early entries. I too balked at the term "senstitivy" as there is no defined spec for sensitivity. For the rest of the thread, in an attempt to match up with the question, I defined sensitivity to be "equal output for a given input" and so, in this discussion the intent was to equate sensitivity with gain, with a clear understanding that this does not define the weak signal performance without accounting for internal and external noise.
All of my numbers and suggestions are based on the receiver system showing a noise rise when the antenna is connected. Only Alan has brought into the conversation the case where internal noise exceeds the antenna noise and my response there is "get a better antenna".
I completely agree, if internal noise it higher than external noise then gain is not the answer. That was not the case in Roger's problem so far.
Warren Allgyer
9V1TD
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Softrock Lite IF and TS-940
Hello all,
I am new to the group and I am in need of help. I have a TS-940 and just ordered a Softrock Lite II IF with the 8.812 IF crystal, on the suggestion of Tony Parks at FiveDash. It is being built for me. I need to know what is the best way to connect the IF from the TS-940 to the SR Lite II. Do I run from the IF out on the radio to the RF in one the SR Lite ?? What I am trying to achieve is the ability to have a panadapter display for my TS-940 and to eventually control the radio through the SDR application. Any help would be appreciated and thank you for your help in advance. BTW, I have on order a Piexx TS-940 interface for CAT control.
Eric? N3DWS
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My mistake. SR RX II input impedance is actually close to 50 ohm.
Thanks to all who have been contributing to this discussion.
I finally figured out why my measurement of the input impedance of the SoftRock Ensemble II differed drastically from what the design would lead one to expect.
Thanks to Warren's suggestion of using a 'scope together with the MFJ 259B, I saw that the 259's output level was 1.2V peak. This exceeds the threshold voltage of the back to back diodes that I had installed on the SR input as a protection against overload. Thus, the MFJ 259B was indicating a low impedance because it was driving the diodes into conduction.
I tacked together an attenuator so that the input voltage was less than .5 Volt and then put a 56 ohm resistor in series. The voltage on the Rx side was just a little less than half that on the high side of the 56 ohm resistor. Thus, the impedance of the Rx input is close to 50 ohm, as expected.
Sorry for the confusion guys.
Now that input mismatch as a possible source for the limited "sensitivity" or noise figure has been eliminated, I can focus on the other issues being discussed. Back later ...
Roger
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Hi Warren,
In the technical literature about receivers, they don't use such parameter as "sensitivity". 2 most important receiver parameters that determine whether you can hear the signal or not are: 1. Gain 2. Internal noise.
There is no point in increasing the gain if the signal is drowned in noise.
Your measured the gain of the system that includes Softrock, soundcard and software. You did not measure the internal noise.
I guess both gain and noise stay more or less flat in the case of Softrock, although both get worse towards 30MHz. So your statement about sensitivity being flat is actually true.
However, the number of stations you can hear also depends on the signal and noise levels coming from the antenna. This is why Softtrock "sensitivity" is more than adequate below 14MHz, but is not good enough above 21MHz. On lower frequencies, external noise dominates and drowns weak signals. On higher bands, it is the internal noise that drowns them. Increasing gain doesn't help in this case. Only a preamp with lower internal noise can help. Or a high gain directional antenna, if you don't need omnidirectional receiving.
73, Mike
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Alan:
....With apologies to the board that Alan and I have once again hijacked a relatively simple inquiry and taken it down a rat hole. On the assumption that this might be helpful or at least entertaining to some, let's descend another level
>Assuming op-amp noise is the problem then this noise is the limiting factor.
I don't assume this at all. In fact it is highly unlikely that op amp noise is a factor at all. Roger correctly characterizes it as "SR output noise" which would be a combination of ambient RF pickup, LO and mixer noise, and op amp noise. The contribution of the op amps is barely measurable and is negligible. Pulling power from the SR kills all of the noise contributing stages, not just the op amps. If you want to measure the op amp noise then simple pull the USB connection to the LO. This shuts down the LO and, therefore, the mixer as well as any ambient RF pickup. What remains is indeed op amp noise and I challenge you to find more than a dB or 2 even on your EM-U. If you do find some it will be in the -155 to -160 dBm range and not a factor in anything.
>Roger has said "So, the SR output noise level is 10 dB above my sound card¡¯s noise floor." This is not >antenna noise, seems to confirm the op-amp noise is more than the soundcard noise.
It is much more likely "system" noise than op-amp noise but that is picking nits in this context. Yes, his sound card seems to have a lower noise floor than does the SR.
>Your advice to increase sensitivity by increasing soundcard gain will
not work if antenna noise is covered by >op-amp noise. Provided the antenna or Softrock noise is seen any increase in soundcard gain just reduces >dynamic range.
The only measurements Roger has provided show antenna noise higher than system noise. Anecdotally he mentioned that sometimes there is not a noticeable antenna noise increase but did not measure under those conditions. My suggestion that he increase the sound card gain until the noise increases was based on the assumption there was still a slight amount of antenna noise detectable but too low to measure. I would have been more complete to say "Increase the sound card gain until you see a measurable noise increase. Then disconnect the antenna and see if it goes down". If it does not then a preamp might help but a better antenna would be the best solution.
>If reducing the gain of the op-amps reduces their noise and if that noise was more than antenna noise then >there is actually an increase in sensitivity.
Absolutely not. Reducing the gain of the op amps also reduces the signal level by a corresponding amount. Adding gain later will correspondingly increase the noise to no net benefit.? The only positive effect of reducing the op amp gain is to improve the large signal handling capability of the stage. And this is only effective if the soundcard has more headroom than the op amp... they usually do.
The bottom line is this:
If connecting the antenna at 24 MHz does not raise the noise level in HDSDR then one of three things is happening:
1) You need a better antenna (clearly not the case for Roger)
2) There is some unaccounted for loss in the front end or mixers in the SR.
3) You live in a much quieter location than I have yet encountered and you need to consider #1 or a preamp.
#2 is easily eliminated in Roger's case by using the MFJ as described in my earlier post.
Warren Allgyer
9V1TD
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Original Message ----- Subject: Re: [softrock40] Re: softrock40
For a given signal level:
The same sensitivity (gain) produces the same output.
Increased sensitivity produces increased output.
Reducing the op amp gain reduces the sensitivity but can increase the dynamic range.
Warren, Assuming op-amp noise is the problem then this noise is the limiting factor. Roger has said "So, the SR output noise level is 10 dB above my sound card¡¯s noise floor." This is not antenna noise, seems to confirm the op-amp noise is more than the soundcard noise. Your advice to increase sensitivity by increasing soundcard gain will not work if antenna noise is covered by op-amp noise. Provided the antenna or Softrock noise is seen any increase in soundcard gain just reduces dynamic range. If reducing the gain of the op-amps reduces their noise and if that noise was more than antenna noise then there is actually an increase in sensitivity. Up to 10dB might be possible using the spare 10dB but only if the op-amp noise is reduced by 10dB and it is the only factor involved. . Or, if quieter opamps were used then there would again be increased sensitivity for the same gain. I guess this would be true even if there was significant loss in the front end, providing the front end is not contributing noise. Roger has said that when conditions are quiet he sees no antenna noise. This is what I find. On 12m and 10m a Norton 8dB antenna preamp rectifies this situation, it may not be the best solution but I think it the easiest I do not always use low noise soundcards so I have not fully investigated reducing op-amp gain. I am not talking about improving on the SNR seen at the antenna terminals. But if this is degraded by a noisy device or attenuation before the first device this can be rectified. No doubt there is an ideal noise figure (or MDS) for a receiver on 10m. I do not think my Softrocks reach that figure. Anyone testing at this time in the sunspot cycle should be wary, I expect there is a high natural noise level there at times. 73 Alan G4ZFQ It is like a ship whose superstructure will not fit under a bridge at high tide. The distance between the water surface and the bridge is the dynamic range. Reducing the op amp gain allows the signal to enter the sound card at low tide, without very strong signals, the superstructure, clipping. If the sound card has enough gain to offset the reduction then the dynamic range is increased. But the "sensitivity" stays the same. Using a low noise card does nothing to improve the weak signal performance at HF. It may significantly improve the large signal
handling capability if used in conjunction with "lowering the tide" by reducing the op amp gain. At HF the signal to noise level
is established in the atmosphere and antenna and cannot be improved by anything you do afterwards. It can be degraded by using
noisy devices downstream but not improved.
Warren Allgyer
9V1TD
---In softrock40@..., <alan4alan@...> wrote :
Original Message -----
Subject: Re: [softrock40] Re: softrock40
Sorry Alan but I have to disagree.
Warren,
What are you disagreeing with?
It, of course, depends on your definition of sensitivity. When a given level of RF input produces the same level of IF output
then, by my definition of sensitivity, the "sensitivity" of the receiver is the same on all bands. And that is the case with the
Softrocks platform. Yes
The only gain in the Softrocks receivers is supplied by the op amps. The op amps operate over the same frequency range no matter
what the operating frequency you choose. The only difference in "sensitivity" for a Softrocks at 28 MHz versus 1.8 MHz is the
loss
in the filters and in the mixer. And, over the range of 2-30 MHz, in a properly built RXII, that difference has been shown to be
negligible.
Yes
The attenuators are in line in the low ranges of the RXII not because the receiver gain or "sensitivity" is greater at those
frequencies, but because high power interference is more prevalent at those frequencies. Once a high power signal is applied to
the op amps to the point that they overload then the overall performance of the receiver is greatly degraded. That can easily
happen from 1-10 MHz.... and rarely above.
No, antenna, atmospheric, noise is far greater on 160m than it is on 20m. So to increase dynamic range anttenuators are required.
And antenna, atmospheric noise is far less on 10m. There can be strong signals on any frequency.
The fact that Roger's RXII does not produce a noise rise at 24 MHz, when his reference receiver does using the same antenna,
indicates that the total gain of the Softrocks system is insufficient to overcome the noise of the sound card. No. It can mean the noise of the Softrock is greater than antenna noise. At least with my Softrocks removing power reduces the
noise floor. The Softrock noise overcomes soundcard noise. Conclusion:- Antenna noise does not overcome Softrock noise.
This has been demonstrated not to be a design problem Has it? Where?
so there is either too much loss in the filter/mixer Possibly
or insufficient gain in the op amp/PC input.
But people, Mobo users in particular, say that reducing op-amp gain reduces op-amp noise thereby increasing the RF
sensitivity/dynamic range with a low noise soundcard.
Or have I got that wrong?
73 Alan G4ZFQ.
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Roger
Just correcting one point I made earlier on the MFJ. It is the danger of working from memory rather than checking notes or actually measuring....
My MFJ-259 was an eBay tech special that I revived. It has a very constant output from 1.7 though at least 50 MHz of about -30 dBm. This is generally low enough that it will not overload the op amps when connected directly into the antenna input.
This makes it an almost ideal signal generator for the Softrocks. The output is high enough to see on a scope if you have one and allows you to check before and after each transformer and tuned circuit. If you put a test lead into the MFJ output connector and use the probe to inject the signal you can start at the mixer, working your way back, while listening and watching the output on HDSDR, and you can very quickly locate the stage or component that is causing a signal loss.
In the RXII in particular it is great to tune across the 4,8,and 16 MHz boundaries and make sure the level stays roughly the same as the filters are switched.
In your case in particular I would do the latter to reassure yourself that one or more of your filters is not bad. You should see the same level from the MFJ on HDSDR at 24 MHz that you see at 14, 7, and all other frequencies.
Good luck once again.
Warren Allgyer
9V1TD
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Roger
So long as you see a noise rise when you connect the antenna your receiver is doing the best job possible for detecting weak signals. Improving the filter input and output matches may marginally improve the system gain or "sensitivity" but will not improve weak signal detection because the signal to noise level is established by antenna and atmospheric noise.
If you do not see a rise in the noise floor when connecting the antenna then you should increase the soundcard gain until you do.
When using HDSDR you can read noise levels using the S meter or by reading the level on either of the spectrum displays. You will note that the noise level readings on the spectrum display are dependent on the Resolution Bandwidth (RBW) setting. The displayed noise level is a value integrated across the resolution bandwidth; more bandwidth = higher indicated value. The noise level is not changing, only the bandwidth within which the noise is being measured.
I have one each of the RXTX transceivers and the RXII receiver. All show about the same noise levels of -140 to -145 dBm on HDSDR after calibration so that S9= -73dBm, and using the 0.4 RBW setting with the antenna input terminated in a 50 ohm load. I have a range of sound cards that give noise floors from -160 dBm to -125 without the Softrocks connected. Obviously the system or "op amp" noise shows up on the better sound cards and not on the noisier ones. My antenna noise levels range from -100 to -120 depending upon the band so the sound cards all produce the same signal to noise levels in normal operation.
My recommendation is turn up your PC input gain until the noise just starts to rise on 24 MHz.
Warren Allgyer
9V1TD
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Alan >But people, Mobo users in particular, say that reducing op-amp gain reduces op-amp noise thereby >increasing the RF sensitivity/dynamic range with a low noise soundcard.
>Or have I got that wrong? For a given signal level: ??? The same sensitivity (gain) produces the same output.
??? Increased sensitivity produces increased output.
Reducing the op amp gain reduces the sensitivity but can increase the dynamic range. It is like a ship whose superstructure will not fit under a bridge at high tide. The distance between the water surface and the bridge is the dynamic range. Reducing the op amp gain allows the signal to enter the sound card at low tide, without very strong signals, the superstructure, clipping. If the sound card has enough gain to offset the reduction then the dynamic range is increased. But the "sensitivity" stays the same.
Using a low noise card does nothing to improve the weak signal performance at HF. It may significantly improve the large signal handling capability if used in conjunction with "lowering the tide" by reducing the op amp gain. At HF the signal to noise level is established in the atmosphere and antenna and cannot be improved by anything you do afterwards. It can be degraded by using noisy devices downstream but not improved.
Warren Allgyer
9V1TD
---In softrock40@..., <alan4alan@...> wrote : Original Message -----
Subject: Re: [softrock40] Re: softrock40
> Sorry Alan but I have to disagree.
>
Warren,
What are you disagreeing with?
> It, of course, depends on your definition of sensitivity. When a given level of RF input produces the same level of IF output
> then, by my definition of sensitivity, the "sensitivity" of the receiver is the same on all bands. And that is the case with the
> Softrocks platform.
Yes
>
> The only gain in the Softrocks receivers is supplied by the op amps. The op amps operate over the same frequency range no matter
> what the operating frequency you choose. The only difference in "sensitivity" for a Softrocks at 28 MHz versus 1.8 MHz is the loss
> in the filters and in the mixer. And, over the range of 2-30 MHz, in a properly built RXII, that difference has been shown to be
> negligible.
>
Yes
> The attenuators are in line in the low ranges of the RXII not because the receiver gain or "sensitivity" is greater at those
> frequencies, but because high power interference is more prevalent at those frequencies. Once a high power signal is applied to
> the op amps to the point that they overload then the overall performance of the receiver is greatly degraded. That can easily
> happen from 1-10 MHz.... and rarely above.
>
No, antenna, atmospheric, noise is far greater on 160m than it is on 20m. So to increase dynamic range anttenuators are required.
And antenna, atmospheric noise is far less on 10m. There can be strong signals on any frequency.
> The fact that Roger's RXII does not produce a noise rise at 24 MHz, when his reference receiver does using the same antenna,
> indicates that the total gain of the Softrocks system is insufficient to overcome the noise of the sound card.
No. It can mean the noise of the Softrock is greater than antenna noise. At least with my Softrocks removing power reduces the
noise floor. The Softrock noise overcomes soundcard noise. Conclusion:- Antenna noise does not overcome Softrock noise.
>This has been demonstrated not to be a design problem
Has it? Where?
>so there is either too much loss in the filter/mixer
Possibly
>or insufficient gain in the op amp/PC input.
>
But people, Mobo users in particular, say that reducing op-amp gain reduces op-amp noise thereby increasing the RF
sensitivity/dynamic range with a low noise soundcard.
Or have I got that wrong?
73 Alan G4ZFQ.
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Original Message ----- Subject: Re: [softrock40] Re: softrock40
Those input impedance measurements make me wonder if changing the T3 turns ratio would improve the sensitivity. Currently the ratio is 8T primary (bandpass filter side) to 4T ctr tapped secondary (2T bifilar, QSD mixer side). Has anyone tried 16:4 or 8:2 which would, it seems to me, increase the input impedance from 8 ohms to 32 ohms? Or 20:4 or 10:2 for 50 ohms?
Roger, I'd try reducing the op-amp's feedback resistors. Around 1k7 would be something like -10dB. The capacitors would need changing to maintain the frequency response but probably not to just test. Then see if the Softrock noise is more than the soundcard noise. But I do not know the effects of altering the input coil ratios. Certainly in VHF practice the actual matching is adjusted for minimum noise rather than to any particular figure. I would not expect it to make much difference, certainly not 6dB. 73 Alan G4ZFQ
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Corrected & new measurements - transformer?
Thanks to Alan, Warren and others for the helpful info and comments.
First, I realized that my previous SWR measurements of the input impedance of the Ensemble II were distorted by using a 4 ft RG58 cable to the MFJ259B.
Here are measurements with it connected directly to the SR with a BNC to UHF adapter.
14.190 mHz: R=7, X=4, SWR=6.5
24.936 mHz: R=8, X=3, SWR=5.9
28.010 mHz: R=16, X=32, SWR=5.0.
Next, in response to Alan¡¯s post, I noted the noise floor levels shown by HDSDR on 12 meters.
I am using a FocusRite Scarlett 2i2 USB sound card, a device intended as a microphone preamp and line input for audio recording. It has adjustable input gain, so the exact levels shown below are relative and would change with changes in the input level controls.
No power to SR II:??? ??? ??? ??? -111dB
power to SR II, but mute line opened:??? -111dB
power to SR II, antenna open or 52 dummy:??? -101dB
2 el 12 mtr yagi at 22 mtrs:??? ??? ??? -95dB
So, the SR output noise level is 10 dB above my sound card¡¯s noise floor.
At the moment, my antenna noise is above the SR by 6 dB. When the yagi is connected to the ICOM 738, with SSB filter, the S mtr is on the S0 pin but bouncing up a bit off the pin. With quieter condx, the S mtr sits on the pin with no movement at all - this is when the SR noise level is higher than my antenna noise.
Those input impedance measurements make me wonder if changing the T3 turns ratio would improve the sensitivity. Currently the ratio is 8T primary (bandpass filter side) to 4T ctr tapped secondary (2T bifilar, QSD mixer side). Has anyone tried 16:4 or 8:2 which would, it seems to me, increase the input impedance from 8 ohms to 32 ohms? Or 20:4 or 10:2 for 50 ohms?
Roger
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Original Message ----- Subject: Re: [softrock40] Re: softrock40 Sorry Alan but I have to disagree.
Warren, What are you disagreeing with? It, of course, depends on your definition of sensitivity. When a given level of RF input produces the same level of IF output then, by my definition of sensitivity, the "sensitivity" of the receiver is the same on all bands. And that is the case with the Softrocks platform. Yes
The only gain in the Softrocks receivers is supplied by the op amps. The op amps operate over the same frequency range no matter what the operating frequency you choose. The only difference in "sensitivity" for a Softrocks at 28 MHz versus 1.8 MHz is the loss in the filters and in the mixer. And, over the range of 2-30 MHz, in a properly built RXII, that difference has been shown to be negligible.
Yes The attenuators are in line in the low ranges of the RXII not because the receiver gain or "sensitivity" is greater at those frequencies, but because high power interference is more prevalent at those frequencies. Once a high power signal is applied to the op amps to the point that they overload then the overall performance of the receiver is greatly degraded. That can easily happen from 1-10 MHz.... and rarely above.
No, antenna, atmospheric, noise is far greater on 160m than it is on 20m. So to increase dynamic range anttenuators are required. And antenna, atmospheric noise is far less on 10m. There can be strong signals on any frequency. The fact that Roger's RXII does not produce a noise rise at 24 MHz, when his reference receiver does using the same antenna, indicates that the total gain of the Softrocks system is insufficient to overcome the noise of the sound card. No. It can mean the noise of the Softrock is greater than antenna noise. At least with my Softrocks removing power reduces the noise floor. The Softrock noise overcomes soundcard noise. Conclusion:- Antenna noise does not overcome Softrock noise. This has been demonstrated not to be a design problem Has it? Where? so there is either too much loss in the filter/mixer Possibly or insufficient gain in the op amp/PC input.
But people, Mobo users in particular, say that reducing op-amp gain reduces op-amp noise thereby increasing the RF sensitivity/dynamic range with a low noise soundcard. Or have I got that wrong? 73 Alan G4ZFQ.
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Re: HDSDR - FLDIGI and RXTX Ensemble
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Troubleshooting RXTX Ensemble current-drain problem
Hello--
I assembled an RXTX Ensemble for a fellow radio amateur who
suffers from impaired vision. At an appropriate stage, I measured the
current drawn from the 12-volt power supply and found it to be
approximately 70 mA instead of approximately 24 mA as specified
in the assembly instructions.
I removed the 5-volt regulator and found it to be okay. Measuring
the unpowered 5-volt line's resistance to ground, I noted approximately
70 ohms resistance.
Finding the problem would be easier if a dead-short circuit existed between
the +5 volt line and ground, but making fractional-ohm relative measurements
at a 70-ohm level isn't too practical.
To find the problem, I attached an ohmmeter between the 5-volt line and ground.
Then I used a can of "freeze spray" to individually chill every component
connected between the 5-volt line and ground.
When I sprayed U5, the 74AC74 clock divider, the resistance increased by several
ohms. Heating the 74AC74's case with the tip of a hot soldering iron decreased
the resistance. Replacing U5 decreased the current drain to the proper range.
73--
Brad AA1IP
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Shirley Dulcey KE1L
Warren Allgyer