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Joshua Tree NP

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brandon

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#1
Can anybody confirm whether 172.675 146.2 PL is linked/or the input to 171.675? I heard a vehicle registration check on this frequency (dispatcher only; ID's as "San Bernardino") and they mentioned locations as Bell Mountain and White Tank. The SoCal Scanner book lists 171.675 as Joshua Tree with 3 different PL tones. I cannot pick up 171.675 from my location to verify.
 
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#3
Can you verify?

Hi ,

Can you guys listen to 417.575 MHz and see if its also the park , possibly a UHF link ? I was picking it up years ago from riverside county and have moved out of the area .

mike
 
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#4
Frequency allocations in the federal UHF band changed on January 1, 2008. Down links are now in the 406.1125 to 410.9875 range and up links are from 415.1125 to 419.9875 range. Spacing between the up link and down link used to be 4 MHz, then 6 MHz, but is now 9 MHz apart. Simplex use is in the 411.0000 to 415.100 0 range. This reflects the conversion to narrow band. So the down link frequency of 417.575 you cited has most likely been changed to a narrow band frequency between 406 and 411 MHz. The only exception to this conversion would be if the NPS had not made the change yet. The federal agencies I monitor have been quite busy this year making the change over, all no later than July.

There is a plan for the conversion to narrow band that shows the new narrow band frequency assignment for each old wide band frequency, or so I have heard second hand from a federal radio tech. I haven't seen the plan so I can't tell you what the new down link frequency is for Joshua National Park is. Before this transition many systems were built so the down link repeated the up link. This is no longer the case on the new systems I have monitored this year.

So the search function must be used in order to find the new link frequencies. Should not be too hard if one is near the park headquarters. Winter time weekends can be busy in Joshua Tree and anyone that can spend a little time near the HQ to find the down link should report back to us. Joshua Tree NP is dispatched by the Federal Interagency Communications Center located at the Supervisor's Office of the San Bernardino National Forest in San Bernardino. This could be another location where the down link can be received, although I don't know if the final link into that center is via microwave or not.
 
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#5
Update

Interesting, I left the scanner searching those ranges . Here is what I found:

415.075 Repeats 166.375
415.475 Repeats 171.475
415.575 Repeats 171.475 (not a typo - diferent link to same VHF as above )
415.525 R "tanker base"

Had a second scanner scan the Joshua tree VHF and UHF link as well . Conditions might be bad right now as neither one broke the squelch all day. I have picked up the VHF beofre from my present location. My records show that 417.575 was/is either Lytle Creek to Rogers peak or Paxton hill to unknown tower. If memory serves, it was the old style tone burst type. Maybe they replaced it with microwave.
 

brandon

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#6
From my notes about 417.575 (last year)
Users discussing a campground and info about lost hikers; "San Bernardino North Entrance". Ref Oynx Peak and Bell. User called this freq "Zone"
Last week I monitored this all day and did not hear a peep. Either it moved as Exsmokey said, offline or the signal isn't reaching my location anymore.
I have also seen 417.575 listed as a link for 166.375 and the Mojave Natural Preserve. Hearing "North entrance" would make me think its some type of park.
 
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#7
Interesting, I left the scanner searching those ranges . Here is what I found:

415.075 Repeats 166.375
415.475 Repeats 171.475
415.575 Repeats 171.475 (not a typo - diferent link to same VHF as above )
415.525 R "tanker base"

Had a second scanner scan the Joshua tree VHF and UHF link as well . Conditions might be bad right now as neither one broke the squelch all day. I have picked up the VHF beofre from my present location. My records show that 417.575 was/is either Lytle Creek to Rogers peak or Paxton hill to unknown tower. If memory serves, it was the old style tone burst type. Maybe they replaced it with microwave.
It looks like the BLM and the Forest Service, which use all the frequencies listed above, have not made the change yet. As the direction was just changed in January the next couple years will be a time of transition and hearing down links on 415 and 417 MHz will still be heard, but could change overnight.

It is interesting to see the air guard link on 415.525 still being used on the San Bernardino NF. This is a very common down link for air guard around California. Its use ended in my local area (Inyo NF) this last spring. It was a nice setup as the down link repeated the up link. I'm not sure why, but this feature has been dropped around here.

Having two or more UHF links for the same frequency would indicate that there is more than one remote base on the San Bernardino NF. I could guess that due to the topography of the Forest, one remote base might be somewhere on the San Jacinto Ranger District south of I-10 and one somewhere in the San Bernardino Mountains. I seem to recall that it is located on a peak in the area of Keller Peak. I have it marked on a map upstairs but getting up there is s big effort so I will leave it unnamed at this point. I might be cleared for putting weight on my left leg in two weeks and conclude the forced bed rest that I have been in since September 3rd.

The San Seavine to Rogers 417 MHz link was replaced with microwave some years ago. When traveling south to visit family I used to listen to this link all over the high desert, but it has been 5 years or more since I've done that. When I first became aware of the 417 link I was amazed that a UHF link could use a path from a peak near Lytle Creek to Rogers without an intervening hop. I was even more surprised to find out that microwave on this path was possible also. 417 MHz was/is used by the Dept. of Interior in many locations.

I think the reference to the "north entrance" must have referred to the entrance to Joshua Tree NP near the Park HQ/Visitor Center near the town of Joshua Tree off Highway 62, if I remember the number correctly. The south entrance that which is accessed off I-10.
 
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#8
SB NF links

Where I am, in Carlsbad, I receive both 415.475MHz and 415.575MHz. However, I receive DIFFERENT traffic on each. The 415.475MHz link repeats SBNF Admin Net 172.225MHz and 415.575MHz repeats the SBNF Forest Net 171.475MHz. I am not sure why socalmike is hearing 171.475MHz traffic on both 415.475MHz and 415.575MHz where he is.

-Mike
 
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#9
Interesting

I guess maybe my location, Im at the base of the cajon pass. FWIW They do NOT repeat at the same time and I get .475 weak.
If you guys are interested lets start another thread. Thanks to Brandon for letting me hijack your original thread.
 
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