Date   

Re: Receiver sensitivity parameter

Phillips
 


I am still trying to get my cotton wool stuffed brain around this parameter.

Does this parameter only apply to receivers with ferrite antennas?  Is this the "missing" piece of the puzzle that has eluded me?  It would explain why a barefoot short ferrite antenna receiver generally has lower specified sensitivity than a long ferrite.

If I follow this line of logic then it would suggest that a ferrite antenna receiver operating at 150KHz would need to be in a field 10 times greater than the same receiver operating at 1,500KHz to deliver the same degree of performance.  This would, in turn, suggest that a ferrite antenna receiver will be roughly three times more effective at the top end of the BCB than at the bottom when operating in fields of the same amplitude.

Am I reasonably correct in following this line or am I talking through a cocked hat?





To: ultralightdx@...
From: ultralightdx@...
Date: Wed, 3 Sep 2014 22:17:13 -0400
Subject: [ultralightdx] Re: Receiver sensitivity parameter

 

Whatis.com says it better then me! "The standard unit of electric field (E-field) strength is the volt per meter (V/m). An E field of 1 V/m is represented by a potential difference of 1 V existing between two points that are 1 m apart. 

The volt per meter, or some fractional unit based on it, is used as a means of specifying the intensity of the electromagnetic field (EM field) produced by a radio transmitter. Although an EM field contains a magnetic (M) component as well as an electric (E) component, the relative field strength of radio signals is easier to measure in free space by sampling only the E component. The magnitude of the E component from a distant radio transmitter is often much less than 1 V/m, and in such cases, fractional units are preferred. One millivolt per meter (mV/m) is equal to 10 -3 V/m; one microvolt per meter (? V/m) is equal to 10 -6 V/m; one nanovolt per meter (nV/m) is equal to 10 -9 V/m; one picovolt per meter (pV/m) is equal to 10 -12V/m.
The magnitude of the E component of a radio wave varies inversely with the distance from the transmitter in a free-space, line-of-sight link. If the distance is doubled, the E-field intensity is cut in half; if the distance increases by a factor of 10, the E-field intensity becomes 1/10 (0.1 times) as great. The E component of an EM field is measured in a single dimension, so the intensity-versus-distance relation is a straight inverse rule, not the inverse-square law."





Sent from Samsung tablet


Re: New station logged 8/31/14

microcode@...
 

On Thu, Sep 04, 2014 at 02:34:31PM -0400, 'richarda@...' richarda@... [ultralightdx] wrote:
I've managed to log a new medium wave station.
Congrats! ... and ditto.

Hearing Voice of Russia from Grigoriopol, Moldova on 1413 KHz now at 19:30
UTC which is about 1100 miles from my QTH. Have a PL-310 on order but it has
not arrived so this station was logged on a new PL-660. According to WRTH
they're running half a megawatt but the signal is still just above the
noise.

Propagation is improving as it gets later. Signal has come up quite a
bit in the last 5 minutes. Fades in and out in a very long cycle as is
typical for long path MW.

Can also hear BBC's Cyprus relay on 1323 KHz in the evenings pretty clearly
but it is very close.

QTH is SE mediterranean

--


New station logged 8/31/14

bbwrwy
 

I've managed to log a new medium wave station.

8/31/14
1239 GMT 750 kHz KSEO, Durant OK (0.22 kW @ 276 km/172 mi). Heard by chance while listening to KMMJ, Lexington NE, with a promo for the University of
Oklahoma vs. University of Tulsa football game "on KSEO" on 9/6/14. It immediately faded out under KMMJ. Faded-in briefly at 1254 with "Good times oldies
are back in Texoma....." Heard on a PL-310ET and 8-inch FSL.

9/4/14
1217 GMT KSEO heard again with song "Dream Weaver", followed by weather forecast for southeast Oklahoma., then faded away at 1220. Heard on a barefoot
SRF-T615.

I must admit I didn't know the station existed until heard on Sunday. Total ULR station #1041 and barefoot #1028.

Good DX.

Richard Allen,
near Perry OK USA.


Re: Receiver sensitivity parameter

Bruce Conti
 

On Thu, Sep 4, 2014 at 6:20 AM, mediumwavedx@... [ultralightdx] <ultralightdx@...> wrote:
  I used dBu-dBµV/m to try to show that they are the same thing. Should have stated dBu (equivalent to dBµV/m)...

My bad.  Sometimes my OCD gets in the way.  I initially read it as dBu minus dBµV/m and my brain immediately got stuck.

--
Bruce Conti
B.A.Conti Photography www.baconti.com
¡BAMLog! www.bamlog.com


Puyallup, WA Ultralight TP's for 9-4

Gary DeBock
 

Hello All,
 
The Asians seem to be a little slow in getting out of the gate this season, and their performance this morning followed the same lackluster pattern. With the exception of 972-HLCA and a few other Koreans, most of them were missing in action.
 
Once again at the 1300 UTC start time a weak collection of Asians was in audio, including 594-JOAK, 603-HLSA, 657-Pyongyang, 972-HLCA and the 1053-Jammer. Shortly after 1300 the big gun 972-HLCA reached a temporary good level with Korean news, and maintained this level for about 10 minutes. The other Asians seemed to be stuck in mediocrity, though, with anemic signals in and out of the noise. 603-HLSA's Korean pop music was ghostly at best, and 657-Pyongyang's typical tirades were lacking in strength. Even the 1053-Jammer had trouble sustaining audio. By far the best signal of the morning was from 972-HLSA, with Korean female speech around 1310. With the exception of a ghostly 594-JOAK all of the Japanese seemed to be in hibernation, as well as all of the Chinese. Overall it was a very forgettable session, and fairly typical of the Asians this week.
 
657  Pyongyang   North Korea   Anemic-sounding tirade barely making it through the noise at 1305
                            http://www.mediafire.com/listen/9qxmrr45mncr717/657-Pyongyang-1305z090414PL380.MP3 
 
972  HLCA   Dangjin, South Korea    Good-level female speech and background music at 1310
                           http://www.mediafire.com/listen/rkfy4ketsyu4o1p/972-HLCA-1310z090414PL380.MP3
 
73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)
7.5" loopstick Tecsun PL-380 Ultralight +
15" FSL antenna
 
 
 
 
    


Re: Receiver sensitivity parameter

josephrot
 

Thank you, Bill... very comfortably confusing. Actually, pretty nicely explained.
 
Joe Rotello / Knoxville, TN / USA


Re: Receiver sensitivity parameter

Michael <michael.setaazul@...>
 

Confusion may also arise from the use of u for µ
when the latter is not readily available on the keyboard.

Michael

----- Original Message ----- From: mediumwavedx

Hi Bruce,
Sorry to confuse.

I used dBu-dBµV/m to try to show that they are the same thing.
Should have stated dBu (equivalent to dBµV/m).
Corrected paragraph:

The modern DSP receivers like the Tecsun PL-380, 310, etc. which employ the Silicon Labs chips,
measure and display dBµV as received at the tuned front end across a load, not dBu (equivalent to
dBµV/m). They call it the RSSI indicator, and erroneously mark it as dBµ on the display [Greek 'mu'
again]). It is not the same measurement as dBu, which is derived from volts or millivolts/meter.
73s,
Bill


Re: Receiver sensitivity parameter

mediumwavedx
 

Hi Bruce,

Sorry to confuse.

I used dBu-dBµV/m to try to show that they are the same thing.

Should have stated dBu (equivalent to dBµV/m).

Corrected paragraph:

The modern DSP receivers like the Tecsun PL-380, 310, etc. which employ the Silicon Labs chips, measure and display dBµV as received at the tuned front end across a load, not dBu (equivalent to dBµV/m). They call it the RSSI indicator, and erroneously mark it as dBµ on the display [Greek 'mu' again]). It is not the same measurement as dBu, which is derived from volts or millivolts/meter.

73s,

Bill
 


Re: Receiver sensitivity parameter

Richard Jones
 

Whatis.com says it better then me! "The standard unit of electric field (E-field) strength is the volt per meter (V/m). An E field of 1 V/m is represented by a potential difference of 1 V existing between two points that are 1 m apart. 

The volt per meter, or some fractional unit based on it, is used as a means of specifying the intensity of the electromagnetic field (EM field) produced by a radio transmitter. Although an EM field contains a magnetic (M) component as well as an electric (E) component, the relative field strength of radio signals is easier to measure in free space by sampling only the E component. The magnitude of the E component from a distant radio transmitter is often much less than 1 V/m, and in such cases, fractional units are preferred. One millivolt per meter (mV/m) is equal to 10 -3 V/m; one microvolt per meter (? V/m) is equal to 10 -6 V/m; one nanovolt per meter (nV/m) is equal to 10 -9 V/m; one picovolt per meter (pV/m) is equal to 10 -12V/m.

The magnitude of the E component of a radio wave varies inversely with the distance from the transmitter in a free-space, line-of-sight link. If the distance is doubled, the E-field intensity is cut in half; if the distance increases by a factor of 10, the E-field intensity becomes 1/10 (0.1 times) as great. The E component of an EM field is measured in a single dimension, so the intensity-versus-distance relation is a straight inverse rule, not the inverse-square law."






Sent from Samsung tablet


IRCA Convention Update

Phil Bytheway <phil_tekno@...>
 

2014 IRCA 50th Anniversary Convention – Billings, Montana

The 2014 IRCA 50th Anniversary Convention will be held in Billings, Montana on September 19th and 20th. John and Nancy Johnson of Mesa, Arizona are your convention hosts and will arrive a couple of days before the convention. The convention will be held at the Lexington Inn & Suites by Vantage located at 3040 King Avenue West. IRCA members are eligible to receive a special room rate of $95.00(US) per night plus 7% Lodging Tax & $1.00(US) TBID fees. A limited block of rooms have been set aside so you will want to make your reservations early. Please mention “IRCA-International Radio Club of America” when making your reservation for the special IRCA member’s rate. You may call them directly at 406-294-9090 or toll-free 1-877-488-4649. You will need to give them a credit card number and check-in and check-out dates. They do offer an airport shuttle. The parking area is quite large. With this rate you will enjoy the following COMPLIMENTARY top quality amenities to enhance your stay

* A 100% SMOKE-FREE and PET FREE to ensure a healthy environment,
* Guest rooms featuring beautiful furniture, sitting areas, spacious bright bathrooms, pillow-top mattresses, upgraded bed and bath linens and exceptionally quiet rooms,
* New Panasonic flat-screen TVs, iHome radios,
* Comfortable and well-lit workspaces with secure high-speed internet desk access,
* Voice mail and free local calls within the (406) area code,
* Free Internet – wired and wireless,
* Indoor swimming pool with hot tub, changing room and outdoor patio, fitness center,
* Hot continental breakfast. Some gluten items available for purchase.

For more information about Lexington Inn & Suites by Vantage go to LexingtonBillings.com

Radio station tours will be scheduled for Friday morning and afternoon. A tour of Connoisseur Media’s stations is almost finalized. Stations include News-talk KYYA-730, ESPN KBLG-910, Sky KRKX-94.1, The Zone KRZN-96.3, MY 105.9 KWMY, and KLPN-106.7 The Planet. Details will be updated as more tours are added. There will also be a tour of KTVQ 2.1 / Billings CW 2.2 on Friday evening to watch a live production of the 10 PM News. Tours are subject to availability of guides and may be subject to change. There will be several talks presented during the convention.

Tentative Schedule (almost complete):

Friday September 19
  8:30 AM – Registrations
  9:30 AM – Leave for station tour
11:30 PM – Open Lunch
  1:30 PM – Leave for KGHL tour
  3:30 PM – Open session
  6 PM – Pizza Ranch – IRCA Goodie Factory picks up the tab
  7:30 PM – John Johnson – Tower site presentation
  8:30 PM – Leave for KTVQ tour, lasting through 10 PM Newscast

Saturday September 20
10 AM – Mark Durenberger – D-CAS antenna
11 AM – Pat Martin – TP DX
12-2 PM – Open Lunch
  2 PM – Nick Hall-Patch’s presentation by Phil Bytheway
  3 PM – John Johnson reads – “Early IRCA History” by Larry Godwin
  4 PM – IRCA Business meeting
  5 PM – Open session
  6 PM – Banquet – Montana Rib & Chop House
  8 PM – Auction

Hungry? You’ll discover Billings, Montana is filled with numerous places to eat. There is a Johnny Carino’s adjacent to the convention hotel. A few blocks away there is a Pizza Ranch where we will gather on Friday evening. IRCA will pay for this event. Pizza Ranch is a buffet facility featuring pizza and broasted chicken. You can even ask for them to make a pizza your way. The Saturday night convention banquet will be held at the Montana Rib and Chop House.

Registration for club* members is just $35.00(US) (Does NOT include the banquet – details of the banquet will be announced later). Non-club member’s registration is $50.00(US) which includes a one year membership in the IRCA. (Hint: Save money, a one year membership in the IRCA is less than the increased registration fee for non-members. Join the IRCA now.) You may pay in advance by check or PayPal. If paying by PayPal, please add $1.00(US) to cover the $1.34(US) additional charges added on by PayPal. Use this PayPal address: john@... and include a message that the money if for the IRCA convention registration. If paying via check, make that out to John C Johnson and mail to 2922 S Olivewood, Mesa, AZ 85212-2923.

* Club membership in IRCA, NRC, or WTFDA qualifies for the $35.00(US) registration fee. Non club members are encouraged to join the IRCA.

Check out the IRCA Facebook site too! If you have any questions please contact John Johnson at john@....

Phil Bytheway
IRCA President / Goodie Factory
Seattle WA
Drake R-7 / KIWA Loop


Re: Receiver sensitivity parameter

Bruce Conti
 

On Wed, Sep 3, 2014 at 5:48 PM, mediumwavedx@... [ultralightdx] <ultralightdx@...> wrote:

The modern DSP receivers like the Tecsun PL-380, 310, etc. which employ the Silicon Labs chips, measure and display dBµV as received at the tuned front end across a load, not dBu-dBµV/m. They call it the RSSI indicator, and erroneously mark it as dBµ on the display [Greek 'mu' again]). It is not the same measurement as dBu-dBµV/m, which is derived from volts or millivolts/meter.

Now I'm confused.  Nice description of dBu and dBµV/m, but you lost me by introducing dBu-dBµV/m without explanation.  What is dBu-dBµV/m?

--
Bruce Conti
B.A.Conti Photography www.baconti.com
¡BAMLog! www.bamlog.com


Re: Receiver sensitivity parameter

mediumwavedx
 

This can be a confusing subject, so please allow me to offer this explanation.

The common unit used in measuring received field strength is volts per meter, or usually, millivolts/meter 'mV/m' (one-thousandth of a volt per meter).

Volts or millivolts per meter expresses the voltage that would be induced in a one meter long wire placed parallel to the lines of flux of the received signal (remember the electrical flux from a mediumwave tower is vertical, the magnetic horizontal). This induced voltage results from the movement of the flux across the wire.

There is some confusion which persists about the term dBµ, which is related to mV/m.

dBµ, a contraction of dBµV/m, using the Greek letter µ ['mu', meaning micro, or one-millionth], is commonly and usually written nowadays as dBu [letter 'u'] and is the figure used in recent years by the FCC for measuring electric field intensity of AM broadcast stations at prescribed distances. dBu is electric field intensity and directly related to mV/m, always measured in decibels above (or below) one microvolt/meter. The decibel measurement is a logarithmic ratio as you may know.

dBµ ['mu' again] is also sometimes used erroneously as a shortened form of dBµV, or voltage expressed in dB above (or below) one microvolt into a specific load impedance, commonly 50 ohms. Important! Here we have voltage measured across a specific load impedance like a tuned circuit or reactance or resistor.

The modern DSP receivers like the Tecsun PL-380, 310, etc. which employ the Silicon Labs chips, measure and display dBµV as received at the tuned front end across a load, not dBu-dBµV/m. They call it the RSSI indicator, and erroneously mark it as dBµ on the display [Greek 'mu' again]). It is not the same measurement as dBu-dBµV/m, which is derived from volts or millivolts/meter.

You cannot convert dBuV as shown on the DSP radios to mV/m or dBu! The value is not interchangeable.

The FCC offers a conversion calculator to convert from dBu [letter 'u'] to mV/m and back.

http://transition.fcc.gov/mb/audio/bickel/findvalues.html

Or, you can figure it yourself by using the following formula:
dBu = 20 * Log(mV/m * 1000)
To reverse the computation, converting dBu back to mV/m:
mV/m = (10 ^ (dBu / 20)) / 1000

(Log is base 10)

Bill
RADIO-TIMETRAVELLER


Puyallup, WA Ultralight TP's for 9-3

Gary DeBock
 

Hello All,
 
Another fairly mediocre band presented itself this morning, although in an improvement over yesterday a much greater variety of Asians managed some form of weak audio. Vibrant audio was scarce, however, and none of the TP's could manage it for more than a few seconds at a time  during sunrise enhancement.
 
My session started off at 1300 with a pretty diverse collection of Asians already in weak audio-- 594-JOAK, 603-HLSA, 693-JOAB, 972-HLCA, 1044-CRI, the 1053-Jammer.and 1134-KBS. With the exception of the 1053-Jammer all of these anemic signals stayed at a fairly weak level, though, and bailed early around 1325  Unlike most mornings there didn't really seem to be any propagation trend toward favored TP areas-- they were all equally mediocre. Only the 1053-Jammer reached a good level for more than a few seconds, although both 594-JOAK and 972-HLCA had their brief peaks of decent strength from 1305-1310. Like some DXers (including me), the Asians seem to be a little slow in getting untracked for the new season.
 
1053  Korean Jammer   Good buzz at 1305; best TP signal of the morning
 
73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)
7.5" loopstick Tecsun PL-380 Ultralight +
15" FSL antenna
 
 
 
 
   


Re: Receiver sensitivity parameter

josephrot
 

In trying to "simplify" an answer, engineers may get more "complicated"...

Signal strength is typically expressed in voltage per length or signal power received by a reference antenna. High-powered transmissions, such as those used in broadcasting, are expressed in dB-millivolts per metre / meter as the unit of length (dBmV/m).

In the case of low-power systems, such as mobile phones, signal strength is usually expressed in dB-microvolts per metre (dBµV/m) or in decibels above a reference level of one milliwatt (dBm).

Now, we have reached: In broadcasting terminology, 1 mV/m is 1000 µV/m or 60 dBµ (often written dBu), where again, m refers to metre / meter as the unit of length.

Hope this helps...but please don't throw anything at me...:)...

Joe Rotello / Knoxville, TN / USA


Opportunity to log a new station - WVLZ AM 1180

gmosherat
 

Ultralight dx'ers,


Last few evenngs I've head oldies under WHAM 1180 - got a ID tonight - WVLZ AM 1180 Knoxville, TN.  Info on the internet is they changed format from sports to oldies on Aug 29th and are supposed to be day only.


They are copyable here in western NY (home of WHAM). 


Anyone else catch them?


Gpsfool


Receiver sensitivity parameter

Phillips
 

A receiver's LW and MW sensitivity is often specified in mV/M.  What does this actually mean?  I have tried to find out on the web but have yet to find an answer that I can understand.

I presume it means millivolts per metre.  Millivolts I understand but to what does the metre refer?  Does it refer to the wavelength of the received signal?  Does it mean that a receiver, with a MW sensitivity of 1mV/M tuned to a frequency of 1Mhz, has a raw sensitivity of 300mV?  Or does it calculate in some other way?

Can anyone please enlighten me?



Puyallup, WA Ultralight TP's for 9-2

Gary DeBock
 

Hello All,
 
Asian results here were somewhat similar to those reported by Dennis as the TP's struggled back from the recent unsettled solar conditions. Yesterday's star 738-Tahiti was long gone, but three Korean and Chinese stations managed fair to good audio right in the middle of the band from 1305-1320. One of these was 1044-CRI-- a rather unusual station to be received during lackluster propagation.
 
My session started off at 1300, when even decent TP carriers were scarce. Around 1303 the Korean big gun 972-HLCA came into fair audio through "Freedom 970" splatter, followed shortly by 1044-CRI and the 1053-Jammer. Oddly enough, none of the low or high band Asians were managing any audio at all during this period. 972-HLCA's music and 1044-CRI's Japanese service reached fair levels during peaks, while the 1053-Jammer was the only Asian to hit a good level during the morning here. These three diehards bailed out around 1325, wrapping up a fairly bizarre session.
 
1044  CRI   Changzhou, China   Japanese service at fair level around 1307; strange catch during anemic propagation
 
1053  Korean Jammer   Good-level buzz of domestic splatter at 1317; best Asian signal of the morning
 
73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)
7.5" loopstick tecsun PL-380 ULtralight +
15" DXpedition FSL antenna
 
 
                  
 


Re: Predicting MW Intermod/Bleedthrough

Michael <michael.setaazul@...>
 

Yep, I dream of a proper FSL....

But almost any front-end selection will help significantly.
A well-built tunable loop inductively coupled to even a lowly
radio will work wonders by dint of its notch-like tuning, directivity
and gain.

Michael

----- Original Message ----- From: Bruce Conti


If the problem is a wide-as-a-barndoor receiver front end, then maybe
you should invest in one of those monster DeBock FSL antennas.
This type of tuned antenna will knock down much of the interference
while peaking the desired frequency, except anything from an external source
like the 1010/1050 product. To further narrow the bandpass would require
the external antenna connected to a positive feedback RF amp like the Connelly MWT-3.


Re: Predicting MW Intermod/Bleedthrough

Bruce Conti
 

If the problem is a wide-as-a-barndoor receiver front end, then maybe you should invest in one of those monster DeBock FSL antennas.  This type of tuned antenna will knock down much of the interference while peaking the desired frequency, except anything from an external source like the 1010/1050 product.  To further narrow the bandpass would require the external antenna connected to a positive feedback RF amp like the Connelly MWT-3.

--
Bruce Conti
B.A.Conti Photography www.baconti.com
¡BAMLog! www.bamlog.com


Re: Predicting MW Intermod/Bleedthrough

Michael <michael.setaazul@...>
 

----- Original Message ----- From: mediumwavedx

I find that the weak point of the newer DSP radios seems to be desense
more than anything else. I think it comes from an inadequate front end.
It does little to have a 1 KHz filter further downline in the receiver chain
if the front end is desensitized by strong local signals. The filter (and radio)
works great out in the boondocks, but bring it to the city near several
5 KW - 50 KW stations and the desense is apparent for +/- 50 KHz sometimes.
Couple that with the soft-mute irritant and you are basically blanked out for a width of 100 KHz.

________________________________________________

Spot-on! Many receivers, including high-spec amateur radio transceivers,
incorporate a barn-door front-end for design and production convenience.
This allows everything with a few uV to surge in and infect even sophisticated
signal processing further down the chain.

If we buy into this market, we must expect to be duped. But we can up-front
the front-end with vicious selectivity - sigh...

PS : If you have local AM power-houses, be grateful. In the Old World, our
medium-wave transmitters are being culled at an alarming rate.

Michael

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