Date   

West coast of Scotland server back up

John
 

Folks,
Some things fixed after the power outage last week.
New and splendid kevlar cored antenna stretched 100m across the bay.
Winter storm resistant with a bit of luck.
Also - RFI lines on waterfall have gone away - forever we hope.

Airspy 2 + Spyverter:

sdr://tumbril.asuscomm.com:5555/

Very limited internet bandwidth - 4 users only.
For the moment the first user gets to control gain.
The reason for this is that MW and LW are red hot and may need turning down; others up bit perhaps.
Gain opens at '4'
May fix gain in future - suggestions for level appreciated.

Server will go off for some time tomorrow for some cable work and then back on by about 4pm for the the next few weeks at least.
Well that's the plan anyway...

Be handy to know if everything is working satisfactorily.

Thanks,

John


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

David Eckhardt
 

CONNECTORS (off topic for AirSpy, but we wandered into connector territory):

I once attempted Heising modulation for lack of a large modulation transformer.  But I had a large 'filter' choke which was rated for twice the voltage and lots of Henries to form a choke for audio frequencies.  For those who are unaware, Heising modulation produces a constant current.  That means that the voltage, if given the opportunity to break down, sores as high as it needs to maintain the current draw until the magnetic energy stored in the inductor is drained. 

The rig was all home brew consisting of a pair of 813's modulated by a pair of 811's.  The 811's had been retired from RF service due to too much RF for the thin plates (holes in plates) to endure.  The power supply sourced 1.9 kV under load at a bit over an ampere.  I used an HN (that's a high voltage N-conmnector) on each end of the cable to connect the HV supply to the modulator and RF deck.

Well,..........., if you've ever experienced a constant current dump from a large inductor, you will NEVER forget the experience (and might need a change of underware).  The HN, for some reason (probably sloppy cable termination at the connector on the part of the author) broke down and threw a lasting blue and thick discharge out the PS end of the connector for some 6 to 8-inches into the room.  What was so different than a capacitor input filter is that there was no 'snap' or bright flash which didn't last.  This darn thing must have lasted a bit over 5-seconds!  That was the end of my wandering into Heising modulation!!

Everyone should have the experience!!!!!

Dave - WØLEV 

On Sat, Nov 18, 2017 at 8:58 PM, jdow <jdow@...> wrote:
1 kW = E^2/50 -> E = sqrt( 50000 ) which is about (off the top of my head) 225 Vrms or a bit over 300V peak. DC rating on these connectors is well over 1 kV. At RF it may arc sooner. But it's very probably safe. (Current is no problem as the connector mass averages the peaks down to the 5W level.)

{^_^}

On 2017-11-18 13:07, Carlos Cabezas Prudencio wrote:
Even for pulsed use, you cant (or you should not) use an under rated connector or coaxial cable, as their power limit is not only determined by their loss or power dissipation but also by their dielectric voltage breakdown. If you get up to that voltage, the duty cycle doesnt really matter and it will arc.

Regards,
Carlos EB4FBZ

El 18 nov. 2017 9:36 p. m., "doug" <dmcgarrett@... <mailto:dmcgarrett@...et>> escribió:


    On 11/17/2017 10:15 PM, jdow wrote:

            As a working RF engineer, in some 1 GHz RF designs, I have used TNC
            at around a KW peak rf power, with semi-rigid coax. Proved out and
            tested in Mil-Spec test routines.


        Gutsy. For radar pulses I might do that. For continuous duty the cables
        would be room heaters until they melted. {^_-}

      Well, these WERE a form of  pulsed RF, with an average power of about 5
    Watts. The connector type was determined by the requirements of the device
    it was
    mated to--which I no longer remember!

    --doug, WA2SAY






--
Dave - WØLEV
Just Let Darwin Work


Re: Down converter hack

Monroe K
 

Yes, I do understand that may be somewhat of a delima? Hummm I would
think on the antenna side but that may not be true I suppose.

Monroe

-------- Original Message --------
Subject: Re: [airspy] Down converter hack
From: "PMM" <pmmeasures@gmail.com>
Date: Sat, November 18, 2017 4:27 pm
To: main@airspy.groups.io


Unfortunately not had any experience yet with my sup2400 due to moving
house last year, not sure how best to test and validate but has been
mentioned in places a lna helpful but not at what stage.

sup2400 NF is 3.5 so most lna's under that but uncertain if lna needed
after I.e. between sup and sdr or before between antenna. or both sides.

Unit itself will work and downconvert it's also used as an upconverter by
hams.

I think the chap that did that article now selling them himself pre modded
though I did mine myself and referenced www.m0dts.co.uk/index.php?item=90
which I think was the upconvetor MOD that made it's basis for using as a
downconvertor.



On 18 Nov 2017 23:07, "Monroe K" <monroe@teamprometheus.org> wrote:

Is there an LNA you could recommend?

Monroe

-------- Original Message --------
Subject: Re: [airspy] Down converter hack
From: "PMM" <pmmeasures@gmail.com>
Date: Sat, November 18, 2017 3:26 pm
To: main@airspy.groups.io


Yes, but may need a lna to recover signal losses on Amy sdr.

On 18 Nov 2017 19:53, "Monroe K" <monroe@teamprometheus.org> wrote:

http://www.kd0cq.com/2016/04/sdr-hack-receive-up-to-4-5ghz-
on-your-rtlsdr-for-5-00/

Have you guy's seen this? I should work with the airspy right?

Monroe






Re: Down converter hack

PMM
 

Unfortunately not had any experience yet with my sup2400 due to moving house last year, not sure how best to test and validate but has been mentioned in places a lna helpful but not at what stage.

sup2400 NF is 3.5 so most lna's under that but uncertain if lna needed after I.e. between sup and sdr or before between antenna.  or both sides.

Unit itself will work and downconvert it's also used as an upconverter by hams.

I think the chap that did that article now selling them himself pre modded though I did mine myself and referenced www.m0dts.co.uk/index.php?item=90 which I think was the upconvetor MOD that made it's basis for using as a downconvertor.



On 18 Nov 2017 23:07, "Monroe K" <monroe@...> wrote:
Is there an LNA you could recommend?

Monroe

> -------- Original Message --------
> Subject: Re: [airspy] Down converter hack
> From: "PMM" <pmmeasures@...>
> Date: Sat, November 18, 2017 3:26 pm
> To: main@airspy.groups.io
>
>
> Yes, but may need a lna to recover signal losses on Amy sdr.
>
> On 18 Nov 2017 19:53, "Monroe K" <monroe@...> wrote:
>
> > http://www.kd0cq.com/2016/04/sdr-hack-receive-up-to-4-5ghz-
> > on-your-rtlsdr-for-5-00/
> >
> > Have you guy's seen this? I should work with the airspy right?
> >
> > Monroe
> >
> >
> >
> >
> >
> >





Re: Down converter hack

Airspy US
 

We have a wideband preamp but it's only spec'ed to 4 GHz.

<<https://v3.airspy.us/product/upu-fpwb/>>

---------
Airspy.US
Your USA source for quality SDR products!
www.Airspy.US

NOTE! This email address is not routinely monitored.
If you have an issue, please contact us at airspy@airspy.us

On 11/18/2017 6:07 PM, Monroe K wrote:
Is there an LNA you could recommend?

Monroe

-------- Original Message --------
Subject: Re: [airspy] Down converter hack
From: "PMM" <pmmeasures@gmail.com>
Date: Sat, November 18, 2017 3:26 pm
To: main@airspy.groups.io


Yes, but may need a lna to recover signal losses on Amy sdr.

On 18 Nov 2017 19:53, "Monroe K" <monroe@teamprometheus.org> wrote:

http://www.kd0cq.com/2016/04/sdr-hack-receive-up-to-4-5ghz-
on-your-rtlsdr-for-5-00/

Have you guy's seen this? I should work with the airspy right?

Monroe






---
This email has been checked for viruses by AVG.
http://www.avg.com


Re: Down converter hack

Monroe K
 

Is there an LNA you could recommend?

Monroe

-------- Original Message --------
Subject: Re: [airspy] Down converter hack
From: "PMM" <pmmeasures@gmail.com>
Date: Sat, November 18, 2017 3:26 pm
To: main@airspy.groups.io


Yes, but may need a lna to recover signal losses on Amy sdr.

On 18 Nov 2017 19:53, "Monroe K" <monroe@teamprometheus.org> wrote:

http://www.kd0cq.com/2016/04/sdr-hack-receive-up-to-4-5ghz-
on-your-rtlsdr-for-5-00/

Have you guy's seen this? I should work with the airspy right?

Monroe






Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

jdow
 

1 kW = E^2/50 -> E = sqrt( 50000 ) which is about (off the top of my head) 225 Vrms or a bit over 300V peak. DC rating on these connectors is well over 1 kV. At RF it may arc sooner. But it's very probably safe. (Current is no problem as the connector mass averages the peaks down to the 5W level.)

{^_^}

On 2017-11-18 13:07, Carlos Cabezas Prudencio wrote:
Even for pulsed use, you cant (or you should not) use an under rated connector or coaxial cable, as their power limit is not only determined by their loss or power dissipation but also by their dielectric voltage breakdown. If you get up to that voltage, the duty cycle doesnt really matter and it will arc.
Regards,
Carlos EB4FBZ
El 18 nov. 2017 9:36 p. m., "doug" <dmcgarrett@optonline.net <mailto:dmcgarrett@optonline.net>> escribió:
On 11/17/2017 10:15 PM, jdow wrote:
As a working RF engineer, in some 1 GHz RF designs, I have used TNC
at around a KW peak rf power, with semi-rigid coax. Proved out and
tested in Mil-Spec test routines.
Gutsy. For radar pulses I might do that. For continuous duty the cables
would be room heaters until they melted. {^_-}
 Well, these WERE a form of  pulsed RF, with an average power of about 5
Watts. The connector type was determined by the requirements of the device
it was
mated to--which I no longer remember!
--doug, WA2SAY


Re: Down converter hack

PMM
 

Yes, but may need a lna to recover signal losses on Amy sdr. 

On 18 Nov 2017 19:53, "Monroe K" <monroe@...> wrote:
http://www.kd0cq.com/2016/04/sdr-hack-receive-up-to-4-5ghz-on-your-rtlsdr-for-5-00/

Have you guy's seen this? I should work with the airspy right?

Monroe






Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

doug
 


On 11/18/2017 04:07 PM, Carlos Cabezas Prudencio wrote:
Even for pulsed use, you cant (or you should not) use an under rated connector or coaxial cable, as their power limit is not only determined by their loss or power dissipation but also by their dielectric voltage breakdown. If you get up to that voltage, the duty cycle doesnt really matter and it will arc.
It worked. Probably is still working today--it was a test set.
--doug

Regards,
Carlos EB4FBZ

El 18 nov. 2017 9:36 p. m., "doug" <dmcgarrett@...> escribió:

On 11/17/2017 10:15 PM, jdow wrote:
As a working RF engineer, in some 1 GHz RF designs, I have used TNC at around a KW peak rf power, with semi-rigid coax. Proved out and tested in Mil-Spec test routines.

Gutsy. For radar pulses I might do that. For continuous duty the cables would be room heaters until they melted. {^_-}
 Well, these WERE a form of  pulsed RF, with an average power of about 5 Watts. The connector type was determined by the requirements of the device it was
mated to--which I no longer remember!

--doug, WA2SAY





Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Carlos Cabezas
 

Even for pulsed use, you cant (or you should not) use an under rated connector or coaxial cable, as their power limit is not only determined by their loss or power dissipation but also by their dielectric voltage breakdown. If you get up to that voltage, the duty cycle doesnt really matter and it will arc.

Regards,
Carlos EB4FBZ

El 18 nov. 2017 9:36 p. m., "doug" <dmcgarrett@...> escribió:

On 11/17/2017 10:15 PM, jdow wrote:
As a working RF engineer, in some 1 GHz RF designs, I have used TNC at around a KW peak rf power, with semi-rigid coax. Proved out and tested in Mil-Spec test routines.

Gutsy. For radar pulses I might do that. For continuous duty the cables would be room heaters until they melted. {^_-}
 Well, these WERE a form of  pulsed RF, with an average power of about 5 Watts. The connector type was determined by the requirements of the device it was
mated to--which I no longer remember!

--doug, WA2SAY




Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

doug
 

On 11/17/2017 10:15 PM, jdow wrote:
As a working RF engineer, in some 1 GHz RF designs, I have used TNC at around a KW peak rf power, with semi-rigid coax. Proved out and tested in Mil-Spec test routines.
Gutsy. For radar pulses I might do that. For continuous duty the cables would be room heaters until they melted. {^_-}
Well, these WERE a form of pulsed RF, with an average power of about 5 Watts. The connector type was determined by the requirements of the device it was
mated to--which I no longer remember!

--doug, WA2SAY


Down converter hack

Monroe K
 

http://www.kd0cq.com/2016/04/sdr-hack-receive-up-to-4-5ghz-on-your-rtlsdr-for-5-00/

Have you guy's seen this? I should work with the airspy right?

Monroe


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Leif Asbrink
 

Hello Ruben,

In the 130 to 150 MHz range the antenna noise temperature
is near room temp. If you want optimum performance it would
be a good idea to go for a system noise temperature well below
room temperature to make the noise in your output originate
in the antenna with negligible noise from your receiver.

This means that a system NF of 1 dB or less is desireable.
I do not remember the NF of the Airspy R2, you might
try to look it up, I would guess it is something like 5 dB
which would mean a system NF of about 6.5 dB. If you would
use a LNA with NF=0.5 dB your S/N would improve by about 6 dB.
That is a significant improvement. The drawback is that
your dynamic range would be degraded.

If LNA gain is 23 dB and system NF improvement 6 dB, the noise
floor would increase by 17 dB when you apply power to the LNA.
That is what an EME operator (moonbounce) would want because
the system NF would be about 0.1 dB above the LNA NF. The
dynamic range is however deggraded by 17 dB. You might insert
a 7 dB attenuator to gain 7 dB dynamic range while loosing
about 1 dB of S/N in case dynamic range is a problem.

It is probably a better alternative to reduce the gain of the
R2 to degrade its NF by about 6 dB to get to a state where
the noise floor change when you power on/off the LNA is about
13 dB. Whether to use Linearity or Sensitivity depends on
whether offending signals are within the visible frequency range.

73

Leif

Hello friends:
My knowledge of RF concepts are medium to low.
I am learning a lot reading this group.
Here are some thinkings about my setup at this moment:

Using an Airspy R2.
Main use are frequencies from 130 to 150 Mhz (Mainly 137 SAT Frequencies).
I am using:
Antenna --> Around 6 meters CO22 Coax Cable--> LNA with HPF and BPF included for 137.5Mhz ( https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94 ) --> 30 meters Ecoflex 10 Coax cable --> Airspy R2

Ecoflex 10 has an attenuation of around 5db in 100m. Then i will have 1.5db of attenuation in 30 meters.
Lets estimate a loss in connectors and converters of around 1 db more ¿? ----> Then i have around 2.5db of total attenuation.

With this calculation i think my LNA has too much gain. (M anufacturer talks about 23db gain).
Is this correct?
I will have best results with a 15db attenuator after the LNA.

I am having the best results using GAIN 10 and Linearity.
What do you think about all this?

Thank's a lot.


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

jdow
 

If you see no signs of overload with no LNA then leave it out. It saves power. You're greener or something like that. If you have nearby large signals from time to time the SAW filter in that LNA may help. You know your local conditions, I don't. So all I can do is conjecture and that's not what you want.

One caveat here - the S+N/N ratio you should test at is something on the order of 6 db to 9 dB to have the greatest sensitivity to overall sensitivity differences. Testing at 20 dB or 30 dB is not so good. Of course, testing at 50 dB is usually worthless.

{^_^}

On 2017-11-18 10:49, Ruben Navarro Huedo (EA5BZ) wrote:
Hello again:
This evening i was playing and doing some tests.
I have around the same SNR with and without my LNA+HPF+SAW BPF ( https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94 )
This is how i did the test:
I used my VNA connected to a little whip-antenna to generate an ON-AIR reference signal of 137.5 Mhz.
With my Airspy connected to my turnstile i played with gain to have the best SNR.
Then i did the same without the VNA and SNR were around the same.
Whit this test result i think the best is NOT use LNA.
What do you think?
Thank's again :-)


Re: New SpyServer optimizations and features #spyserver

Jon Fear
 

@Martin - G8JNJ

Many thanks for the tip on an attenuator however looking into my issues I realised that I was 4DME from the Clevedon TX outputting 50KW of BBC Radio 5 goodness. A rather quick purchase of an AM BC filter appears to have sorted that. Just doing some final checks tonight, hopefully put my SDR's online tomorrow...

Jon


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Ruben Navarro Huedo (EA5BZ)
 

Hello again:

This evening i was playing and doing some tests.
I have around the same SNR with and without my LNA+HPF+SAW BPF ( https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94 )
This is how i did the test: 
I used my VNA connected to a little whip-antenna to generate an ON-AIR reference signal of 137.5 Mhz.
With my Airspy connected to my turnstile i played with gain to have the best SNR.
Then i did the same without the VNA and SNR were around the same.

Whit this test result i think the best is NOT use LNA.

What do you think?

Thank's again :-)


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

David Ranch
 


I'd like to understand why some commercial radio vendors ship their new radios to EU countries with N-connectors but their US versions ship with UHF connectors?  Why?!

The only thing I've heard good about UHF connectors in the past is their power handling capabilities.  Though not needed from a leakage or loss perspective, how does say an N or TNC connector do at 1500 watts @ HF frequencies with say a 2:1 match?

--David
KI6ZHD


On 11/17/2017 05:46 PM, doug wrote:
BNC is rated to 400 MHz. I have used TNC up to 1 GHZ on some MIL-STD hardware I designed. I don't remember its specified frequency rating.
I think the RF construction (as against the physical construction) of the two types (N or BNC) is not very different, at least when connecting either one to a coax like
LMR 240. For LMR 400, I would not like a conversion to BNC. If you need LMR 400, for most purposes you should stay with type N. BTW: BNC connectors definitely
leak RF at higher VHF frequencies. If you are concerned about RF leakage from a smaller coax coax connector, you might consider TNC. It's not very popular, it seems,
but it is a screw-type version of BNC, and is more RF-tight.  If you have sensitive receivers and need to keep rf out, don't use BNC. This is a job for TNC or SMA.

(I used to use TNC and coax for medium voltage DC connections in my ham shack using 50 Ohm coax, back when stations were modular--say 1965.)

As a working RF engineer, in some 1 GHz RF designs, I have used TNC at around a KW peak rf power, with semi-rigid coax. Proved out and tested in Mil-Spec test routines.

Join my crusade against UHF connectors! Let's get them out of ham radio! They're over 75 years old, designed when the best RF engineers were just trying to get
their arms around COAX CABLE. I don't think the MIT papers were even out yet.



locked This week's Twitter game #airspyhfplus

prog
 


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

Joe M.
 

I think you meant 4000 MHz (AKA 4 GHz).

<<https://www.amphenolrf.com/connectors/bnc.html>>

Joe M.

On 11/17/2017 8:46 PM, doug wrote:

BNC is rated to 400 MHz.

--doug, WA2SAY


Re: Some calculations about GAIN, LNA, ATTENUATORS, COAX...

jdow
 

On 2017-11-17 17:46, doug wrote:
On 11/17/2017 08:06 PM, Eric Oyen wrote:
agreed on the UHF connectors. the problem is they are the most marketed connector out there.

btw, waveguide? any way you slice it, that is going to get expensive! Hardline of the 3/8ths inch variety would make a cheaper alternative (but at $3 per foot, its still insane).

now, other connectors that are lower loss start with the N connector. expensive but guaranteed up through 3 Ghz. BNC might make a more viable uhf type, so long as you don't go too far above 500 Mhz. many others are available, but not sure on specs or cost.

DE n7zzt Eric

BNC is rated to 400 MHz.
Slipped a decimal point there, keno sabe.

I have used TNC up to 1 GHZ on some MIL-STD hardware I designed. I don't remember its specified frequency rating.
0 to 11 GHz - chiefly due to the more rigid connection. Both N and TNC "die" about where the 3/8' and 1/4" cables become hybrid waveguide/coax assemblies.

I think the RF construction (as against the physical construction) of the two types (N or BNC) is not very different
In a severe pinch you can cut the outer shell with its bayonet construction off the male BNC and mate it to a female N. It works the other way, too, but the cutting is harder. (Kids, don't try this at home. This is for trained professionals only. And replace BOTH connectors ASAP. This is strictly a temporary setup. (No, don't ask.))

If you need LMR 400, for most purposes you should stay with type N.
Use N for power handling and physical connection strength. Use BNC if you have to made with an existing BNC connector. Use SMA if required. (annecdote warning) We discovered on the GPS prelaunch test receiver that you CANNOT assemble the versions of RG223U (double shielded 1/4") type N connectors that were available in the 70s with a low VSWR at GPS frequencies. Both above and below GPS frequencies it worked fine. We ended up switching to N to SMA bulkhead connectors with SMA to RG223U cable used inside the test set. The kludge had an adequate SWR, something like 1.1 vs 1.7 to 2 if I recall correctly.

BTW: BNC connectors definitely
leak RF at higher VHF frequencies.
Well, that varies with how straight you keep the connection. That's where TNC shines as it's more rigid when mated.

In all cases go to wave guide if the power involved exceeds the power handling capacity of the coax alternatives at the frequency of interest. (1 kW is not going to be happy in 1/4" cable at any frequency let alone 1 GHz.)

As a working RF engineer, in some 1 GHz RF designs, I have used TNC at around a KW peak rf power, with semi-rigid coax. Proved out and tested in Mil-Spec test routines.
Gutsy. For radar pulses I might do that. For continuous duty the cables would be room heaters until they melted. {^_-}

Join my crusade against UHF connectors! Let's get them out of ham radio! They're over 75 years old, designed when the best RF engineers were just trying to get
their arms around COAX CABLE. I don't think the MIT papers were even out yet.
1930s or so, I believe. (Wikipiddle more or less agrees with my memory.) Most pieces of equipment around here got the UHF connectors ripped off and N's installed. They mate just a whole lot better than the iffishness of the UHF maybe-connector. I might use UHF connectors for high voltage DC connectors with the SO239 on the power supply end of a hard wired cable on the power consumer end. Just don't spill a drink on it.

--doug, WA2SAY
{^_-} Joanne, who'd also like to modify all audio connections to differential pairs. Ban the mini-plug and mini-hack er jack.

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