AM/FM broadcast interference on 80M

G3DEN

Just a quick question, I have been getting AM or FM broadcast station interference on 80M nothing has changed with the station I am using an end fed 160M antenna at around 50ft

I cannot seem to get rid of the issue.

Any idea's?

Richard
G3DEN

John KB4DU

Are you running multiple slices on multiple bands? If so, the radio will be in wide mode. Running only one slice on 80M should engage the filters, depending on which radio in use.

G3DEN

I am running a single slice on a 6400 on a single band only V3.2.31 of the software with a Maestro, the antenna is a 160M end fed antenna.

Stan VA7NF

May be a different case.

Listening to the received signal, are there TWO stations heard?

I have been chasing the source of the mixing of two broadcast band stations (by a diode/rust) somewhere in the area. If there are two, direction finding on the mixing product should show the source but it is not working in this case.

Also, for example, when transmitting on 80M 3700 I hear a signal on the second harmonic 7400Khz + 600Khz BC station

G3DEN

There seems to be two stations on the received audio. I am living near brokmans park in the UK, there is a big transmitting station there it is a BBC station

Erik Carling EI4KF

I think you will find that the transmitter location is Brookmans Park and is currently the subject of other complaints. You should contact RTIS https://www.radioandtvhelp.co.uk/what-are-you-having-problems-with and, in theory anyway, they will liaise with the site engineers. If not, it will be a matter for Ofcom. It would be sensible to verify that the 6400 is not at fault by checking with another radio prior to lodging the observation.

WX7Y

That is a hard problem with the 6400 and 6600 radio , if it where the 6700 it already has receive loops that allows you to STACK external filters like Broadcast Filters specifically built for things like this before it hits the radio receiver BUT as it is you could try to come up with a couple antenna relays that switch the filter out of line during Transmit, MFJ makes some of these MFJ-1708-SDR-S RF Sense SDR receiver Transmit/Receive Switch transceiver Switch if you wire two of these up you could build a external Broadcast filter setup to switch the filters in and out of line during TX/RX that may just help but first thing to do is pick up or build a HIGH quality Broadcast filter or two to try out when your receiving, DON'T transmit through them as these are low power devices if they work then this is what the MFJ-1708's will be used for if the B.C. Filters get rid of the majority of the Broadcast harmonics and let you operate. DLW associates build the DLW-FL1718 and is a brick wall one or there are some el-cheep-o's that RTL-SDR.COM builds but not sure how good.

UPDATE just checked the specs and the DLW-FL1718 it WILL pass 200W RF TX so you won't need to have the by-pass relays just the DLW filter

JUST A THOUGHT

Mike-VA3MW

I just want to reword what Bret said just a bit (I have to think of this from a marketing perspective).

The 6700 has a receive loop built into the radio that allows you to insert preamps and filters in the receive chain. Look at connectors labeled 12.

That hardware design was not part of the 6400 and 6600 series as there wasn't enough user demand to have it and to add the expense of building it in.

73

Stan VA7NF

Richard,

You confirmed hearing two stations mixed together.

The problem is likely external to your receiver; confirm this by:

• Since you know one of the two, subtract that frequency from the receive address, that should be the other CB station.
• Look for other mixing products by adding the BBC station with other BC stations - Each of those combinations should result in another case.
• If an external filter or changing the RF gain does not make the mixing product disappear then that confirms the signal is external. If it is then no front end filters will fix the problem as the signal is really on the frequency you hear.
• Try using a short-wave battery radio that has directional antenna and try to find where the mixing product comes from.

Good luck.

Stan

Lasse SM5GLC

Richard, do you have the gain i.e. pre-amp/attenuation at the antenn settings,a, a bit too high?

I would set the slider as far to the right as possible and see it the interference is still there.

/Lasse SM5GLC