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Ham transceiver as LW RX

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#1
Many Ham transceivers have general coverage receive capability which in some cases extends to AM BCB and below.
My question would be based on your actual experience, what ham transceiver have you found to be a good performer as a LW receiver?

Thought this may be a useful exercise given the recent interest in Ham longwave.

FWIW, the Alinco DX-SR8T does an amazing job as a LW receiver. Have logged hundreds of NDBs with it. Overall, a lot of radio for the money.
 
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#2
I've no experience of "other" transceivers but do have an Alinco DX-R8 receiver covering 30kHz to 35MHz. For the money it is a pretty good unit. If the SR8 and SR9 transceivers perform like the R8 (I see no reason why not as the R8 is just an SR9 without the transmitter circuitry) then I'm with you on the capability and value for money.

I'm looking at getting an SR9, but I'm a little biased as I've created my DriveR8 program which supports the SR8/SR9 and I'd like to spend more time using the kit as opposed to writing a new program for a different piece of equipment.
 
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#4
I've had a few high end premium receivers in the past including a Harris RF-590 and a 590A. I find my Elecraft K3 is superior most of the time and with the options I have it goes down to 100KHz. For MW and VLF I use an AMRAD active whip and a home made 1m loop with preamp.

BTW, one of my Harris receivers had optional phase coherent (or something like that) crystal filters and with its super wide BW up to 16KHz it sounded awesome on AM broadcast and better than the K3.
 
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#5
Be careful when comparing specs. Many radios say they cover down to 100kHz or thereabouts but then when you delve a bit deeper you may find that in fact their sensitivity and intermodulation figures are nowhere near as good as their HF specs. I have a couple of radios which I would call good domestic communications receivers but get them below 500kHz or so and there's birdies and broadcast signals a-plenty. I have another commercial marine receiver designed to cover the NDB's and low frequency time signals and it's a totally different beast - clean as a whistle.
 
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#7
I have an IC-746PRO that I've used on LW. It compares favorably with my ITT Mackay 3041 and Watkins Johnson WJ-8718A. I'm of the opinion that 90% of the work on those frequencies is done by the antenna. I use a W1VLF loop and preamp.
 

spongella

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#8
Longwave listening is certainly lots of fun, what with the aero beacons, the new ham band, lowfers, NAVTEX transmissions, and DGPS-outfitted beacons.

I used to use a Tempo One transceiver with a Palomar LF converter and the combo worked great using a 43 foot vertical. Am currently using a frequency selective levelmeter (Sierra 303B) for LW/BCB listening. Still evaluating how well it works on LF. BCB rx is great though.
 
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#9
Be careful when comparing specs. Many radios say they cover down to 100kHz or thereabouts but then when you delve a bit deeper you may find that in fact their sensitivity and intermodulation figures are nowhere near as good as their HF specs. I have a couple of radios which I would call good domestic communications receivers but get them below 500kHz or so and there's birdies and broadcast signals a-plenty.
Some interesting replies so far...

Anyway, since some of the transceiver RX specs are somewhat vague outside the Ham bands is what prompted me to start this thread to see what actual experience others have had using their transceiver to RX LW.

The Alinco DX-SR8T is spec'ed as 1 uV CW sensitivity below 160 meters which is quite good for a transceiver on LW. Could not find a specific dynamic range or IP3 spec but in actual use, it will receive co-channel beacons on a frequency occupied by a very strong local beacon. Overloading doesn't seem to be a problem. Not a lot of spurs and broadcast band signals either. Overall, a good performer on LW... :)
 
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#10
The Alinco DX-SR8T is spec'ed as 1 uV CW sensitivity below 160 meters
Well, actually it says the SSB sensitivity is 1uV but I suppose you have to infer that the CW sensitivity is about the same. However these figures are useless with quoting a signal-to-noise ratio or signal level out, usually a 10dB signal/noise ratio - but again SSB and CW sig/noise is not just turning off the signal and measuring the noise. Also they didn't quote the bandwidth.
1uV/-107dBm is not startling anyway, my background noise here on short 45 ft wire is about -120dBm/ 0.3uV and an NDB on 242kHz gives me -97dBm/3uV - he's about 60 miles away - on an HP 3586A level meter, at 0800 local time.
There's some nice programmes out there (WSPR etc) that will dig a signal out from under the noise - must give them a try sometime although I think it involves very slow CW and a form of coherent detection.
 
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#11
Well, actually it says the SSB sensitivity is 1uV but I suppose you have to infer that the CW sensitivity is about the same. However these figures are useless with quoting a signal-to-noise ratio or signal level out, usually a 10dB signal/noise ratio - but again SSB and CW sig/noise is not just turning off the signal and measuring the noise. Also they didn't quote the bandwidth.
1uV/-107dBm is not startling anyway, my background noise here on short 45 ft wire is about -120dBm/ 0.3uV and an NDB on 242kHz gives me -97dBm/3uV - he's about 60 miles away - on an HP 3586A level meter, at 0800 local time.
There's some nice programmes out there (WSPR etc) that will dig a signal out from under the noise - must give them a try sometime although I think it involves very slow CW and a form of coherent detection.
That -120dBm sounds nice. The background noise here this evening with all the electronics in the neighborhood spewing their garbage is about -90dBm on 40 meters and about -85dBm on LW (with 500 cycle filter selected).

Anyway, the Alinco manual gives the sensitivity as 1 uV for both SSB and CW below 160M but, as you say, without giving SNR (maybe 10dB S+N/N). In itself, not spectacular but compared to published specs for other Ham transceivers that is a pretty good figure.
 
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#12
Be careful when comparing specs. Many radios say they cover down to 100kHz or thereabouts but then when you delve a bit deeper you may find that in fact their sensitivity and intermodulation figures are nowhere near as good as their HF specs. I have a couple of radios which I would call good domestic communications receivers but get them below 500kHz or so and there's birdies and broadcast signals a-plenty. I have another commercial marine receiver designed to cover the NDB's and low frequency time signals and it's a totally different beast - clean as a whistle.
Marty both my R71a and R75 get MW doubles every 10kHz throughout most of the LW band. Is that the fault of those receivers, or am I just too darn close to the flames?
 
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#13
Hi Ridgy,

Well, it's a combination of the R75 design and the proximity of the flame throwers.

I had a quick scan of the LW band on my R2000 and on 261kHz I got an S7 signal of our local sports programme on 828kHz which was giving me S10+20dB - there were a few other weaker signal on 261kHz too. I guess there's something going on in the mixing process or distortion in the local oscillator waveform.
So I had a look at the schematic for the R2000 and the antenna filter circuit is quite basic - a bandpass filter from150kHz to 1MHz lets everything through so there's nothing to stop 828kHz wreaking havoc and every other station below 1MHz. If you tune above 1MHz then there's another filter 1MHz to 2MHz so there could well be more birdies of AM BC band stations above 1.7MHz.

My NRD515 is quite well behaved as they have alleviated the problem. Below 600kHz signals go through a low pass filter so no BC band can get through. Tune to the BC band and there is a preselector from 600kHz to 1.6MHz to peak up any weak station and it works well in keeping the flame throwers out. Above 1.6MHz the filters are quite narrow compared to the R2000, the first one is only 1.6 to 3MHz.

The Debeg 7313, a proper marine receiver, a rebadged Skanti R5000 designed by Siemens Germany, is totally different. A great deal of attention has be incorporated to keep unwanted signals out, from 60kHz right up to 30MHz there is a quite narrow tunable preselector which peaks up any signal very well, but as soon as you tune about 50kHz away, then you need to retune the preselector. This obeys the long-held idea that you should apply maximum selectivity before any amplification or frequency changing. The LF band is almost free from all birdies and stations in the wrong place, although I suspect my re-alignment some time ago was not the best as it requires an RF voltmeter which I didn't have at the time - but I do now so it may get a going over. The narrow preselector is essential if you are try to establish a true duplex phone call as your transmitter, may be 1kW, is only 300kHz away. Strangely enough, the good old FRG7 has a tunable preselector but the performance of the radio below 500kHz is abysmal! Shame!

Now your R75 is much the same as my R2000. A low pass 1.6MHz filter lets everything through followed by a 10dB attenuator - an attempt to reduce the cross-modulation and other nasties. Unfortunately if you have cut this attenuator out you have made life worse! You can switch in the front panel ATT to put in a 20dB attenuation but that's counter-productive. Above those LF's, you have a 1.6MHz high pass followed by a 2MHz low pass filter so effectively passing 1.6 to 2MHz frequencies, than above that it's much the same, 2 to 4, MHz, 4 to 8 MHz. etc up to 30MHz.

I'm afraid you're stuck with it, unless you can rotate your Wellbrook! Of course, if you see a Yaesu or Kenwood Antenna Tuner grab it with both hands. Although those little tuners are designed to match longwires and other things, if you feed them with 50ohm coax then they just revert to a bandpass tuned filter. Whether they will go down tp LF, I don't know - I feel an experiment coming on..... :)
 
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#14
Ridge,

Couple of thoughts, Take a look at the low pass filter by PAR that has a passband below 500 kc. Universal Radio has it listed in their online catalog. Have no personal experience with this filter but it may be useful in your situation.

Have a MFJ 1020C active antenna here that has been useful as an active preselector especially in conjunction with a homemade loop. It is one of the few out there that tunes down into LW. The only issue is that you have to constantly retune the preselector as you tune the radio dial.

Of course, if you live within a couple of miles of a 50kw blowtorch all bets are off. :(
 
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#15
Hi Ridgy,

Well, it's a combination of the R75 design and the proximity of the flame throwers.

I had a quick scan of the LW band on my R2000 and on 261kHz I got an S7 signal of our local sports programme on 828kHz which was giving me S10+20dB - there were a few other weaker signal on 261kHz too. I guess there's something going on in the mixing process or distortion in the local oscillator waveform.
So I had a look at the schematic for the R2000 and the antenna filter circuit is quite basic - a bandpass filter from150kHz to 1MHz lets everything through so there's nothing to stop 828kHz wreaking havoc and every other station below 1MHz. If you tune above 1MHz then there's another filter 1MHz to 2MHz so there could well be more birdies of AM BC band stations above 1.7MHz.

My NRD515 is quite well behaved as they have alleviated the problem. Below 600kHz signals go through a low pass filter so no BC band can get through. Tune to the BC band and there is a preselector from 600kHz to 1.6MHz to peak up any weak station and it works well in keeping the flame throwers out. Above 1.6MHz the filters are quite narrow compared to the R2000, the first one is only 1.6 to 3MHz.

The Debeg 7313, a proper marine receiver, a rebadged Skanti R5000 designed by Siemens Germany, is totally different. A great deal of attention has be incorporated to keep unwanted signals out, from 60kHz right up to 30MHz there is a quite narrow tunable preselector which peaks up any signal very well, but as soon as you tune about 50kHz away, then you need to retune the preselector. This obeys the long-held idea that you should apply maximum selectivity before any amplification or frequency changing. The LF band is almost free from all birdies and stations in the wrong place, although I suspect my re-alignment some time ago was not the best as it requires an RF voltmeter which I didn't have at the time - but I do now so it may get a going over. The narrow preselector is essential if you are try to establish a true duplex phone call as your transmitter, may be 1kW, is only 300kHz away. Strangely enough, the good old FRG7 has a tunable preselector but the performance of the radio below 500kHz is abysmal! Shame!

Now your R75 is much the same as my R2000. A low pass 1.6MHz filter lets everything through followed by a 10dB attenuator - an attempt to reduce the cross-modulation and other nasties. Unfortunately if you have cut this attenuator out you have made life worse! You can switch in the front panel ATT to put in a 20dB attenuation but that's counter-productive. Above those LF's, you have a 1.6MHz high pass followed by a 2MHz low pass filter so effectively passing 1.6 to 2MHz frequencies, than above that it's much the same, 2 to 4, MHz, 4 to 8 MHz. etc up to 30MHz.

I'm afraid you're stuck with it, unless you can rotate your Wellbrook! Of course, if you see a Yaesu or Kenwood Antenna Tuner grab it with both hands. Although those little tuners are designed to match longwires and other things, if you feed them with 50ohm coax then they just revert to a bandpass tuned filter. Whether they will go down tp LF, I don't know - I feel an experiment coming on..... :)
This MW injection every 10kHz is probably why I can never hear WWVB on 60 like others can. Even when I rotate the Wellbrook it stays in there at a steady s8 in SSB! There are two culprits, 560KSFO and another one I haven't IDed yet. I know KSFO's transmitter is just across town near the bay. And like you said, hitting the ATT kills everything including the good stuff.
Ridge,

Couple of thoughts, Take a look at the low pass filter by PAR that has a passband below 500 kc. Universal Radio has it listed in their online catalog. Have no personal experience with this filter but it may be useful in your situation.

Have a MFJ 1020C active antenna here that has been useful as an active preselector especially in conjunction with a homemade loop. It is one of the few out there that tunes down into LW. The only issue is that you have to constantly retune the preselector as you tune the radio dial.

Of course, if you live within a couple of miles of a 50kw blowtorch all bets are off. :(
Would that low pass filter effect my MW abilities?
 

ka3jjz

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#16
This discussion is interesting, but please note the OP specified ham transceivers in the title.

Discussions on receivers are encouraged along this same line, but please start a new thread

Onward...Mike
 
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#19
This discussion is interesting, but please note the OP specified ham transceivers in the title.

Discussions on receivers are encouraged along this same line, but please start a new thread

Onward...Mike
OK - The OP said transceivers

We potentially have soft conflict here.

I'll use the Alinco DX-SR9 Transceiver here as an example.

Transceivers can be limited to receive on those bands they can transmit on. Others open up the reception to wideband but limit TX to limited bands only.

The OP was, I believe, asking about Transceivers that have decent / extended / etc genral HO coverage for 30kHz to 35+ MHz.
 
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