Lassen VNP
I just returned home from the second part of my Lassen VNP trip, which was mostly in the
Warner Valley/Drakesbad area for 6 days in the SE corner of the park. Returned home Sunday and
Monday via Chester, Mineral, Manzanita Lake (LVNP's west entrance), Mt Shasta City, Yreka, etc.
usfsengine was spot-on with the frequencies for the new LVNP P25 system. Its a mixed mode
analog/P25 digital system with four repeaters linked together. After getting the new freq list from
usfsengine, I programmed my TK-2180 analog FM radio and got both analog and P25 digital traffic
from the Mt Harkness, Turner Mtn and West Prospect Pk repeaters. The Table Mtn repeater is mostly
for the west side of Lassen. Warner Valley is in the SE corner of the park. As rpoole23 said, the PL
tone is 110.9, for both input and output. That's the PL-tone that was used on the old Lassen Peak
repeater. I did not have the capability to retrieve the NAC, so I appreciate rpoole23's posting the NAC.
Dispatching is from the Yosemite dispatch center via a VoIP connection. Sometimes the dispatchers
forgot and responded as "Yosemite" rather than "Lassen" when they were called. In my 6 days or so
monitoring the new freqs, the dispatchers always transmitted in analog mode. While the rangers and
other staff were roughly about 65% analog and 35% digital. Some users seemed to prefer digital while
others mostly preferred analog. As I mostly had my radio set for carrier squelch (CS) receive, I could
hear the dispatcher in analog mode followed by a radio user in "buzzsaw" digital mode, which was of
course unreadable on a TK-2180. With Tone Squelch (TS) enabled then I would only hear the analog
side of the conversation. I.e., no "buzzsaw" digital coming thru the analog radio.
As the repeaters are all linked together, when the dispatcher keys up the transmission goes out on
all four repeaters. And when a radio user keys up, their signal is repeated by all four repeaters.
The system mostly seemed to work OK, but they have problems, including:
a) Radio users call Lassen dispatch, dispatch responded, radio users got poor/no copy. Last
Friday I heard this go thru several cycles, including someone trying to relay. So the "talk-out"
from the repeater was not as good as the "talk-in" in this case. Seemed odd, as the "talk-in"
signal from the radio user was fine when I heard it repeated. Maybe his radio wasn't up to par on
RX. Maybe a linking problem. Maybe intermod, spurs, etc. This happened several times during
my stay.
b) The reverse of the above: Where the Dispatcher called radio users, the users responded,
and dispatch could not copy. This would normally be the more common problem since the
"talk-out" from the repeaters should normally be stronger than the "talk-in" to the repeaters.
But at Lassen, many (maybe all) of the repeaters are solar powered and so their TX ERP is
probably not much stronger than an HT. I heard radio users in this scenario switching
between digital and analog modes to try and "get in." In some cases this worked. Maybe
some repeater desensing going on here, especially given the linking system and very closely
spaced antennas from what I saw at the Mt Harkness site.
c) Radio users complained about the coverage being poorer in P25 digital mode than when in
analog mode. No surprise there. Especially in rough terrain when the path is often non-LOS.
Multi-path induced ISI, especially at low C/N.
d) All the P25 HT radios I saw were Bendix-King types. The users were whining about them
eating batteries. Indeed, I heard one radio user ask another to bring a replacement battery
to a meeting they were arranging. No surprise on this problem since most P25 radios pull
from 100-ma to 300-ma in squelched receive (standby) mode. 3 to 10X more than what a
good analog radio draws. I dunno, but I wouldn't be surprised if LVNP doesn't have a
battery maintenance program to test/resuscitate their HT radio batteries. With power sucking
P25 radios this is a necessity.
e) Some radio users were not speaking closely into their mikes and had very low TX audio.
f) I often heard lots of background chatter while the Yosemite based dispatchers were
transmitting.
g) The Forest Service, from what I was told, is staying analog FM. So there are interoperability
issues -- especially when LVNP radio users are transmitting in P25 digital mode, the FS
radio users can't copy them, unless they have a digital capable radio. Dunno what the situation
is with the FS fire fighters on the ground, Cal Fire, etc. Maybe usfsengine can enlighten us?
I did an 8-mile hike (16-miles round-trip) from the Warner Valley campground to the top of Mt Harkness.
Which included a 2800-ft climb in a 4.1-mile stretch. The Mt Harkness repeater equipment installation is
a bit sloppy, especially the antenna installation. There are 4-ea half-wave loop folded dipole antennas,
2-wide stacked 2-high. Plus a UHF yagi. The dipoles are very close together and thus have much
mutual coupling, pattern distortion, etc -- especially those that are broadside to each other.
Presumably one dipole is used for the Mt Harkness repeater and the others are used for linking with the
other three repeaters, but I don't really know. The 3-element UHF yagi was pointed down into the
Warner Valley area, 2800-ft below, presumably towards Drakesbad, but I don't really know. Or maybe
they're linking on UHF and the four VHF folded dipoles are supposed to be a directional array for the
park area. But the spacing looks terrible.
I think the new system is an improvement over what they had before with three repeaters (Lassen Peak,
Mt Harkness, West Prospect Peak) all on the same close-spaced pair using separate input PL tones.
In that system, the Lassen Peak repeater had the widest coverage and most use. I've made several
winter trips to Lassen and none of these repeaters worked during the winter in the areas I visited.
Presumably they weren't getting enough sun to keep the batteries charged up. It will be interesting to
see how much of the new system works in the winter.
The West Prospect Peak repeater has excellent coverage outside the park, including as far north
as the Burney area. Turner Mtn has a solid signal west of Morgan Summit (where SR-89/36 meet),
i.e., in the Mineral area (where park headquarters is located). Turner Mt and Mt Harkness are OK
along SR-36 from Chester to Morgan Summit, but there was noticeable mobile flutter and some deep
fades in analog mode with a roof top 1/4-wave antenna on my camper. And probably some occasional
P25 dropouts, gurgling sounding audio, etc Mt Harkness and West Prospect Peak were good along
SR-89 inside the park from the SW entrance to Summit Lake. Table Mtn and West Prospect Pk were
best in the NW area around Manzanita Lake, Chaos Crags, and Sunflower Flats. Radio users in
the Horseshoe Lake backcountry and Juniper Lake areas also sounded good on Mt Harkness in analog
mode.
NPS really needs to improve the repeater antenna systems. They love the folded dipoles and
monopoles for their ruggedness, DC shorted in high electric fields, etc. But they really need
some modest amount of gain for these low TX RF power repeater sites. Stacked phased dipoles with
some electrical downtilt is desirable to put more signal on the ground in the service areas rather than
out into space... They should also do some performance testing, i.e., check the analog MDS and
the P25 threshold for 5% BER to see what their effective front-end noise figure is like. Then work
to reduce front-end losses and lower the effective NF. And some path tests would be desirable to
ensure that the overall system, including the antennas, are working properly.
See the attached pictures... Note that the last picture, DSC_4187, was taken a year ago after a
storm rolled thru the area -- note the reduction in blue haze compared to this year's pictures.
Finally, I was lucky to get out the Manzanita Lake entrance station without being nailed by 8437
and his partner, 8431. They had some busy afternoons nailing speeders entering/leaving the park
at the Manzanita Lake entrance station. Must be a revenue enhancement program.
--Larry, W7JYJ
