Transmitter third harmonic received?

[Geordie McBoyne]

Another radio receiver to find out if the 3rd harmonic of the 1152Khz station can be received.
The radio is another made for export model, an all transistor Pye PE12TBQ.
Sure enough, the Greatest Hits station is coming through loud but not so clear because of that distortion. The Pye has a an extendable rod aerial for SW and a ferrite rod for MW reception.
Simple frequency changer using a single OC170 transistor.

Geordie McBoyne.

[Geordie McBoyne]

Peter Scott wrote: "I guess my thoughts were a bit silly given the likely signal sizes. I was just amazed that a broadcaster would be putting out blatant harmonics. Connecting a sig gen at 1152kHz to the aerial input would be interesting."

Hi Peter,
connected the signal generator to the aerial sockets of the two receivers, the 3rd harmonic is very weak. Connected an external aerial to the Pye and the 3rd harmonic, if if is that, from the radio station is even stronger.

Geordie McBoyne.

[Mike Watterson]

Simple frequency changer using a single OC170 transistor.

Which would easily internally generate a 3rd harmonic with a strong signal. Any single transistor mixer/oscillator is much less trustworthy than a DK96 or similar Octode which is much less trustworthy than a triode-hexode. It's why some better transistor sets had separate mixers and oscillators.

The question is how strong is the local station and if there is a 3rd harmonic, how many dB less?

I think the question can't easily be answered without professional gear, maybe a real spectrum analyser. I'd not trust the results of any cheap SDR as they have notoriously poor RF selectivity and dynamic range (less than 20 dB).

Somewhere on Ofcom there will be a spec for spurious emissions of a MW transmitter. I always thought Lisnagarvey is very close to Lisburn and most MW sets behaved strangely near it.

[Geordie McBoyne]

The Greenside transmitter is in the Gateshead MBC area is located as the crow flies only 2miles from my home address. According to mediumwaveradio.com/uk the power is 1800watts.
In some radio receivers this station breaks through on the long waveband.
I agree this might well be a problem with type of mixer-oscillator circuits employed in the receivers under discussion.
From the MB12 transmitter gallery: http://tx.mb21.co.uk/gallery/gallerypage.php?txid=1521

Geordie McBoyne.

[Mike Watterson]

Even a rusty joint or bolt on a mast can generate 3rd harmonics. It could be the transmitter as I'd not expect it to be particularly distorted if it was a receiver issue.

Tell whoever maintains it.

[Murphyv310]

Hi.
I tried this today with the magnetic loop aerial and my Sdrplay RSP1A and on the second harmonic there is a definite line on the waterfall on SDRuno (2304Khz) and occasionally a weak line 3456 khz the third harmonic. Clyde 2 from Glasgow is also on 1152hkz but I effectively nulled it out on the fundamental, looking at the harmonics the weak harmonics are not from Clyde 2 and they disappear when the loop is at the null direction for Newcastle. I'll try again later when its dark assuming the equipment survives the impending lightening storm!!!!!!

[Murphyv310]

Just checked this again.
The carriers that were seen earlier have now disappeared. I'll try later with the XHdata connected to the loop in the house but I doubt there will be anything.

[Geordie McBoyne]

Geordie McBoyne wrote: In some radio receivers this station breaks through on the long waveband."

On the Dynatron TP15 "Commodore" transistor radio receiver. the local 1152Khz station is breaking through on the long waveband frequency of 212Khz 
The AM IF frequency is 470Khz.                                                                                             
  It works out it's 1152 minus  2 X IF.

Geordie McBoyne.

[Murphyv310]

Hi.
Nothing later last night at all.
It's either too weak here or possibly images in the receivers. Have a feeling though it's a TX issue.
Can you not fire up one of the Racal RA17s you have?