JT65 clash with AM on 160M

[VK5LG]

Hello,
historically here in SA there has been a Thursday night [7.30 local] AM net on 1.843 using antique and old school home-brew crystal locked equipment.

Sometimes the sked begins well but becomes unusable due to very strong JT65 signals on about 1.840. I am relatively new to amateur radio and do not want to offend anybody. What I don't quite understand is why JT65 signals exist above 1.815M contrary to the band plan.

I wonder do JT65 operators monitor the frequencies to see if they are interfering with others, or in digital modes is that now not necessary?

Apart form everyone in the AM group buying new crystals for a new frequency, does anyone have a polite suggestion?

73s VK5LG

[VK3ALB]

Have you decoded the JT65 to find out the parties involved? Send one or both a polite email telling them of your plight. They may not be aware of the problem.

[VK6ADF]

The international JT65 HF frequency for top band is 1838 kHz USB as the main frequency and 1805 kHz as an alternate. I expect the majority of the world would be on 1838 kHz so that's why that frequency is in use.

There is a good chance the operators would not be actually listening and just looking at data on screen. I know when I operated digital modes I either had the audio down low or speaker turned off. Also would depend if it's operating having QSO's (probably unlikely on top band) or operating in a beacon mode and in that case it's probably unattended and has been online for a while.

You, or someone else, will probably have to do as Lou suggests.

[VK3HJ]

Your AM receivers on 1843 kHz will likely pick up anything +/- 4 or 5 kHz or more.
Best you could do is narrow your receiver bandpass, or just listen to the upper sideband.
I wouldn't expect the digital ops on the recognised frequency to admit liability for interference, or even be aware of your wideband transmission.
Good luck,
Luke VK3HJ

[VK5ACY]

Many/most radios commonly used on Thursday night are home-brew, ex-commercial or ex-military etc., with no available means
of/to "narrow your receiver bandpass, or just listen to the upper sideband." Most are crystal-locked on 1843KHz....umm..
how does this fit into the band plan.(?)

The VK5 Thursday night AM Net has been running for over 25 years but only lasts for an hour or two from 1930 CST, so if the digital
mode users were simply informed they might RX-only for this short time....if they were like me in 'trying to get along'.

I often operate on Thursday nights and the low-power AM stations from Adelaide at ~100km are often 'clobbered' by the digital signals,
but I can use other receivers and/or my RX-only wood-framed loop to ease the 'problem'...so unless the (especially JT65) digital
signals are running high power I can't complain. The Adelaide area operators can usually hear each other fine due to their close
proximity, and some don't even notice the JT65 - or these digital signals are below their local (city PLI, plasma TV and etc.) noise level.

At my location (around 100km from town) hearing the low-power AM stations (10W-20W) is possible, but I usually have to run 100W of
carrier/400W PEP to be heard....so it's possible that my AM transmission could upset the digital operators/operations !

As stated, the AM Net goes for under two hours and only one night in the week, so surely we can just "try to get along".

Bill VK5ACY near Bowhill on the Murray River PF95sb.

[VK3RX]

Gasp

You mean JT65 and other digital mode users don't first call or listen to check whether or not a frequency is in use before firing up???

Hooligans.

[VK2KRR]

I dont think there actually on the 1.843 freq, but not far enough away to stop any issues.

The same things used to happen on 160m WSPR which is on 1.8366. If someone comes up on 1.843 or 1.840 on voice it causes issues with reception.

Likewise, WSPR and JT65 operations also clashed. While u can narrow the filter, it still de-senses the freq ur looking at, and when the signals ur looking for on WSPR are particularly weak at times, it means ur unable to hear them.

I have emailed Joe K1JT about the issues on 160m band, months ago now, but never had any response back.

[VK3YE]

Just came back from the beach with the mag loop listening for VK5s on 160m AM. One station had an audible carrier but others didn't. He'd have been audible if using SSB but no audio on AM.

[VK3HJ]

Australian Band Plan shows Digital modes from 1800-1810 kHz, but up to 1815 kHz to accommodate DX.
Phone emissions should not extend below 1840 kHz outside daylight.
The new JT and other digital modes on 1838 kHz seem to be a "new" trend, but our local band plan has not caught up with it (yet).
So, I would suggest the only solution would be some give and take by both parties.
I suspect the AM signals will have little effect on the digital signals anyway.
73 es GL,
Luke VK3HJ

[VK6ADF]

I suspect the AM signals will have little effect on the digital signals anyway.

Yes I would think the JT65HF operators would not even be aware of AM transmissions as probably unattended.

As far as I know, the band plan is only a suggestion, and nothing binds anyone from operating differently. As you said though, operating modes happen quicker than those planning band plans can accomodate them and there are so many different digital modes, the suggested digital sections on band plans need to be be constantly changing or don't have them. Just 2, CW and other modes.

[VK5BC]

I'm probably one of the JT65 operators that may have caused problems to the AM net. As has been suggested I wan't aware of any AM stations on 1.843 whilst using JT65, I along with other VK5's & VK3's were working W's & VE's with JT65 without any interferance from the AM stations.

I'm very surprised to find that there is an AM net on 1843 as I always thought that frequency was the unofficial call frequency and I have heard other AM nets above 1850.

I know there is an issue between the WSPR frequency 8 JT65 frequency, I have experience interferance from JT65 stations whilst running WSPR.

The band bands obviously haven't caught up with the frequencies used for these new digital modes and probably needs revising to incorporate what appears to be international agreed frequencies for these modes. I think there is plenty of room above 1850 for those who wish to run AM nets, most of the CW seems to happen below 1830 and most of the SSB between 1840 & 1850.

In the meantime I will be mindfull of AM in the lower portion of 1840 - 1850 but the band conditions don't allow contacts to NA & Canada everynight and you need to take advantage of conditions when they are available.

73's brian
VK5BC

[VK3ZL]

Hi all..The frequency of 1.838 has been used for digital transmissions by quite a lot of hams internationally for quite some time and naturally VK hams have adopted the trend..As a full time CW operator on Topband I am aware of both the local and
international hams are very active there as well as 1.810...Most of the CW DX activity is between 1.815 and 1.835, so Digital modes really have no effect on CW ops..

One would think that there is plenty of room for all modes of transmission on an under utilised band such as Topband and operators respect each others rights to use the band....The WIA made a new band plan around 2002 that has served all operators with no conflicts between users since that time...Over the years and with digital modes now an established operation, I am sure that everyone can cooperate and respect other users..

73..Bob..VK3ZL..

[VK5LG]

Appreciate all who have responded with suggestions, and "Hi" to Bow-Hill Bill. Hopefully some digital operators are now aware of the VK5 AM net on 1.843 thursday nights, for which we are not asking for special consideration, but just to be aware that for an hour a week there is an AM net trying to get through. It ain't called "antique modulation" for nothing. thanks, Greg.

[VK3ALB]

It's my understanding that 1843 is popular due to the availability of cheap crystals. Quite useful when building homebrew gear for 160m. Perhaps it's not the same in the US and running digital modes on 1838 is less of a problem.

[VK5LG]

Hi Lou,

The long standing VK5 1.843 AM net has been going continuously for more than 35 years that I know of, and you are correct, - 1.843 was chosen because that is the crystal that was commonly available. Most of these guys are using home-brew AM sets made years ago, and some recently, and are not frequency agile.

1843 has long been recognised as an AM chat frequency in Australia by the long time operators (most have probably died now), in the past, 1825 was the SSB dx "call frequency" then replaced by 1832kc,now who knows???

VK5AAQ and others have been operating on 1843 AM once a week, most weeks ,originally Monday evenings then Thursday evenings, since 1980. Anyone is most welcome to join the AM net.

It is hoped that we can work in harmony to continue that long standing practice which obviously predated JT65's use of the 1.838 frequency, which on upper-sideband extends to 1.841. One difficulty is that digital modes do not appear to be monitored, so many operators would not be aware of any problems to adjacent users. That is all I wanted to do, make operators aware that some problems are caused by unmonitored digital signals.

Thank-you to all

Greg