Why 160m Rarely Appears in Band-Condition Charts

[ak6fp]

I recently started a post on Reddit about HF band conditions (here’s the link), and someone left a great comment asking why 160 m is missing from most band-condition charts — even though it’s included in nearly every modern transceiver.

It’s a good question, and I think it’s worth explaining.

160 m isn’t “forgotten” — it’s just very difficult to represent accurately with the usual space-weather inputs like Solar Flux (SFI), and the planetary A and K indices.

Most HF propagation models — including the one I use at DXLook.com — are tuned around the F- and E-layers, which govern propagation from 80 m up through 10 m.

But 160 m behaves differently — it’s dominated by the D-layer, which absorbs signals during the day, making skywave propagation nearly impossible.

At night, Topband can be great, but that depends much more on:

• Geomagnetic quiet (low K/A)
• Local QRN (lightning and noise)
• Season (winter is best)
• Latitude

Those factors aren’t reflected in SFI or K, so if we added 160 m to a solar-based chart, it would almost always show “Poor” during the day and “Fair → Good” at night under quiet conditions.

So 160 m isn’t ignored — it just doesn’t follow the same physics that most HF condition summaries are based on. Until we have a good way to include noise and seasonal models, it’ll stay a band that rewards patience, timing, and experience.

 

[Captain Kilowatt]

Well 160m is not HF. It is actually MW, medium wave, and is much more like the AM broadcast band than it is like any HF band. It starts only 95 kilohertz above the AM band.

 

[N0NB]

It seems like the past couple of years that 75m has been quite poor during the midday due to high D layer absorption.

 

[Crawdad]

But 160 m behaves differently — it’s dominated by the D-layer, which absorbs signals during the day, making skywave propagation nearly impossible.

That's ok, the antennas are too damn long anyway. You need 40 acres and a mule to put one up and the Gov'ment aren't handing those out anymore

 

[928bolo]

Here is a link to to K9LA's "An Introduction to Operating on 160m" A short read. Only 9 pages. On page 6 he discusses why predicting propagation on 160 is difficult.

https://k9la.us/An_Introduction_to_Operating_on_160m.pdf

This article is over 20 years old so take his description of the band plan, "Gentlemen's Agreement", with a grain of salt. Lots of FT8 on 1840 these days.

 

[Lost Ram]

I really like the 160M band!!! You really have to be pretty dedicated if you want to talk there due to the antenna length issue. I use a multiband 572 foot loop fed with 600 ohm up at 50-70 feet.

 

[N0NB]

That's ok, the antennas are too damn long anyway. You need 40 acres and a mule to put one up and the Gov'ment aren't handing those out anymore

It's not quite that bad.

I hit on a formula a number of years back that has served me well. I use a center fed doublet that is about 3/8 wavelength on 160m (approximately 205 feet) and fed with 450 ohm window lead. In its current iteration the center is at 40 feet and the ends nominally 25 feet above ground. It works quite well.

It has the nice property of loading easily on 80m and 40m.

In a former iteration I had it on a city lot where I had enough room to fit an 80m doublet (133 feet overall) to which I added about 35 feet at each end at a 90 degree angle to the main flat top and tied them off to utility poles. It got me back on 160m for several years.

The key is a big tuner. In this case I use a Palstar AT1500DT, an older model with the internal balun.