UHF Preselector - Revision history

Bryan at 16:05, 4 December 2015

2015-12-04T16:05:25Z

Bryan: /* Method 2: shortening the cap length */

2015-12-04T16:03:12Z

Method 2: shortening the cap length

Bryan at 15:47, 4 December 2015

2015-12-04T15:47:13Z

Bryan at 04:17, 4 December 2015

2015-12-04T04:17:03Z

Bryan at 04:06, 4 December 2015

2015-12-04T04:06:34Z

Bryan at 23:07, 3 December 2015

2015-12-03T23:07:22Z

Bryan: Created page with "= Basics = The UHF preselector is a 3 pole, low insertion loss (1.2 dB) 4 MHz wide filter. In practice this is closer to 5MHz wide. The preselector varies based on the band..."

2015-12-03T21:30:43Z

Created page with "= Basics = The UHF preselector is a 3 pole, low insertion loss (1.2 dB) 4 MHz wide filter. In practice this is closer to 5MHz wide. The preselector varies based on the band..."

New page

= Basics =
The UHF preselector is a 3 pole, low insertion loss (1.2 dB) 4 MHz wide filter. In practice this is closer to 5MHz wide.

The preselector varies based on the band of the RX as follows

{| class="wikitable sortable"
|-
! P/N !! Range !! Description
|-
| CRX4001|| UHF R0 || UHF Preselector 380-433 MHz
|-
| TLE5991 || UHF R1 || UHF Preselector 403-433 MHz
|-
| TLE5992 || UHF R2 || UHF Preselector 438-470 MHz
|-
| TLE5993 || UHF R3 & R4 || UHF Preselector 470-520 MHz
|-
|}

Note R3 and R4 use the same preselector. The preselector hooks up to a

[[File:Preselector front.jpg|thumb|widths=300px|heights=300px|center|Preselector in receiver]]

The internal design of the preselector is basically a tubular inductor and a top capacitance hat. The center of this hat/inductor has a hole into which the tuning screws slide in to/out of. The R0 preselector has a much longer screw, and the front panel has a protective metal part protecting the protruding parts.

[[File:R0 Rx front.jpg|thumb|Range 0 Receiver front]]

The bottom of the preselector has T10 size screws on it and they need to be tightened and loosened in order of the numbers on the bottom plate. Once apart the variance in the length of the cap hat should be noticed showing the range of the preselector.

{| class="wikitable sortable"
|-
! Range !! Cap Hat length (inches)
|-
| UHF R0 ||
|-
| UHF R1 || .880
|-
| UHF R2 || .650
|-
| UHF R3 & R4 ||
|-
|}

[[File:UHF Preselector diagram.png|thumb|UHF Preselector diagram]]

= Modification =

Two styles of modification have been attempted on these preselectors to raise the frequency. Lowering the frequency has not been attempted (ie. R4 to R2), and all focus on moving R0/1 to R2, though the same techniques would work to move to R3/4.

== Shorting the Rod ==

Shortinign the rods was attempted on the first modification of the R0 to R2 preselector. The cap hats were removed and the center rods were ground down .270" on each rod.

This became a problem as the rods are made of silver plated copper plated aluminum, which makes grinding a hard thing to do. It removed the tinned part of the rods where they solder to the cap hats, and the alignment "key" notched into the top of the rods. The final result was a filter which had a bit more ripple and wider than desired, but with good insertion loss.

I suspect the width was changed mostly due to moving the cap hats lower in the housing.

@@ Line 101: / Line 101: @@
 The procedure is as follows:
-# Open the preselector and set aside screws and top case.
+# '''Open the preselector and set aside screws and top case.'''
-# secure the bottom to a work surface and pre-heat the first cap
+# '''Secure the bottom to a work surface and pre-heat the first cap'''
-<gallery mode=packed widths=200px heights=200px class="center">
+<gallery mode=packed widths=300px heights=300px class="center">
 Cap_removal_prep.jpg
 </gallery>
 <ol>
-<li value=3> using a hot air gun heat the first cap up and remove it.</li>
+<li value=3>'''Using a hot air gun heat the first cap up and remove it.'''</li>
-<gallery mode=packed widths=200px heights=200px class="center">
+<gallery mode=packed widths=300px heights=300px class="center">
 Preselector_cap_removal.jpg
 </gallery>
-<li value=4>do the same for the rest of the caps </li>
+<li value=4>'''Do the same for the rest of the caps''' </li>
-# once cooled down it's time to grind the caps <blockquote>
+<li>'''Once cooled down it's time to grind the caps to .650"''' </li>
 <gallery mode=packed widths=300px heights=300px class="center">
 Grinding_the_major_material_off_hat.jpg
 Grinding_detail_fine.jpg
 </gallery>
-I find it's best to score a line around the cap before grinding.  You can also use a band saw to remove the majority of the metal first and then clean it up on the belt/circular sander.  Clean up the rough cut on a fine sander and debur if necessary.
+Remember you can only remove material, so check each corner for proper length.  The length is not that critical (1/16"); try to get it as close a possible.
 <gallery mode=packed widths=300px heights=300px class="center">
 How_to_check_length_of_cap_hat.jpg
 </gallery>
 </blockquote>
-<li value=6>once all caps are the proper length, clean them in water/detergent bath.  Ensure no grindings are left or able to flake off. </li>
+<li value=6>'''Once all caps are the proper length, clean them in water/detergent bath.  Ensure no grindings are left or able to flake off.''' </li>
 <gallery mode=packed widths=300px heights=300px class="center">
 Washing_in_sink.jpg
 </gallery>
-# Set the caps on the stubs, noting the alignment notch.
+<li>'''Set the caps on the stubs, noting the alignment notch.'''  </li>
 <blockquote>
 <gallery mode=packed widths=300px heights=300px class="center">
@@ Line 141: / Line 140: @@
 There is still much play in the alignment, and they may need to be adjusted once reflowed. </blockquote>
-<li value=8>apply a dab of flux to the joint</li>
+<li value=8>'''Apply a dab of flux to the joint'''</li>
-# reflow the solder with the heat gun, and add silver bearing solder to ensure a nice fillet joint.
+<li>'''Reflow the solder with the heat gun, and add silver bearing solder to ensure a nice fillet joint.'''</li>
-<gallery mode=packed widths=200px heights=200px class="center">
+<gallery mode=packed widths=300px heights=300px class="center">
 Special_Silver_bearing_solder_used_on_preselector_parts.jpg
 </gallery>
-<li value=9>do this for all caps</li>
+<li value=10>'''Do this for all caps'''</li>
-# Allow to cool and then deflux the joints
+<li>'''Allow to cool and then deflux the joints'''</li>
-# Reassemble the case, and tighten screws in numerical order.
+<li>'''Reassemble the case, and tighten screws in numerical order.'''</li>
-# test tuning and insertion loss at 438, 454, and 470 MHz.  Loss should be a dB or less at all frequencies.
+'''<li>Test tuning and insertion loss at 438, 454, and 470 MHz.'''  Loss should be a dB or less at all frequencies. </li>
-<gallery mode=packed widths=200px heights=200px class="center">
+<gallery mode=packed widths=300px heights=300px class="center">
-Quantar R1 to R2 uhf RX filter.png|Quantar R1 to R2 uhf RX filter
+Quantar R1 to R2 uhf RX filter.png|Quantar R1 to R2 UHF RX filter
-R1_vs_R2_preselector.jpg|completed
+R1_vs_R2_preselector.jpg|Completed R1 to R2
 Preselector_after_modificaiton_to_R2.jpg
 </gallery>
 </ol>

@@ Line 100: / Line 100: @@
 This is the preferred method to raise the frequency as it's more in line with the construction Motorola uses.
 <gallery mode=packed widths=200px heights=200px class="center">
 Cap_removal_prep.jpg
 Preselector_cap_removal.jpg
-How_to_check_length_of_cap_hat.jpg
+</gallery>
 Grinding_the_major_material_off_hat.jpg
 Grinding_detail_fine.jpg
-R1_vs._R2_capacitance_hats.jpg
+</gallery>
 Special_Silver_bearing_solder_used_on_preselector_parts.jpg
-Preselector_mod.jpg
+</gallery>
 QUANTAR_R0_CONVERT_OVERLAY_ON_R2.png
 </gallery>
+</ol>

← Older revision		Revision as of 04:17, 4 December 2015
Line 99:		Line 99:

	This is the preferred method to raise the frequency as it's more in line with the construction Motorola uses.		This is the preferred method to raise the frequency as it's more in line with the construction Motorola uses.
		+
		+	<gallery mode=packed widths=200px heights=200px class="center">
		+	R1_vs_R2_preselector.jpg
		+	Preselector_after_modificaiton_to_R2.jpg
		+	Washing_in_sink.jpg
		+	Cap_notch_detail.jpg
		+	Cap_removal_prep.jpg
		+	Preselector_cap_removal.jpg
		+	How_to_check_length_of_cap_hat.jpg
		+	Grinding_the_major_material_off_hat.jpg
		+	Grinding_detail_fine.jpg
		+	R1_vs._R2_capacitance_hats.jpg
		+	Special_Silver_bearing_solder_used_on_preselector_parts.jpg
		+	Preselector_mod.jpg
		+
		+	QUANTAR_R0_CONVERT_OVERLAY_ON_R2.png
		+	</gallery>
		+
		+	[[File:10 Quantar R1 to R2 uhf RX filter.png\|thumb\|Quantar R1 to R2 uhf RX filter]]

@@ Line 18: / Line 18: @@
 |}
-Note R3 and R4 use the same preselector.  The preselector hooks up to a
+Note R3 and R4 use the same preselector.  The preselector hooks up to the RX input and can be removed for testing.
 [[File:Preselector front.jpg|thumb|widths=300px|heights=300px|center|Preselector in receiver]]
-The internal design of the preselector is basically a tubular inductor and a top capacitance hat.  The center of this hat/inductor has a hole into which the tuning screws slide in to/out of.  The R0 preselector has a much longer screw, and the front panel has a protective metal part protecting the protruding parts.
+The internal design of the preselector is basically a tubular inductor and a top capacitance hat.  Interesting to note the coupling takes place at the low side vs. the normal high side. The center of this hat/inductor has a hole into which the tuning screws slide in to/out of.  The R0 preselector has a much longer screw, and the front panel has a protective metal part protecting the protruding parts.
 <gallery  widths=300px heights=300px class="center">
@@ Line 40: / Line 40: @@
 | UHF R2 || .650
 |-
-| UHF R3 & R4 ||
+| UHF R3 & R4 || .437*
 |-
 |}
 <gallery mode=packed widths=200px heights=200px class="center">
 R4 and 3 Vs. R0.jpg|R0 in front vs a R3/4 preselector
-R4 and 3 Vs. R0.jpg|thumb|R0 in front vs a R3/4 preselector
+UHF Preselector diagram.png| Preselector diagram
 </gallery>
-File:UHF Preselector diagram.png|thumb|center|UHF Preselector diagram]]
+Patterns of preselectors measured with a spectrum analyzer.  Note the bit of ripple in the pass band.  Motorola sells a probe to be used to align the preselector via alternate peaking and diping it, but it's much easier to tune on a spectrum analyzer/tracking generator.  This has the advantage allowing you to tune for the exact pass band needed.  In many cases it's advantageous to tune the center off of the frequency.  I find it's easy to tune the entire US 440 ham band input range as a CF of 447.5.
 <gallery mode=packed widths=200px heights=200px class="center">
 QUANTAR R2 factory.png|UHF R2
 QUANTAR R0 380 UN MOD.png|Quantar R0 at 380 MHz
-QUANTAR R0 380 UN MOD.png|thumb|Quantar R0 at 380 MHz
+QUANTAR R0 BEFORE MOD 1.png|Quantar R0 at center
-QUANTAR R0 BEFORE MOD 1.png|thumb|Quantar R0 at center
+QUANTAR R0 MAX FREQ.png|Quantar R0 at 437 MHz
-QUANTAR R0 MAX FREQ.png|thumb|Quantar R0 at 437 MHz
+R0 tuning.jpg|Tuning a R0 preselector
 </gallery>
@@ Line 66: / Line 64: @@
 Two styles of modification have been attempted on these preselectors to raise the frequency.  Lowering the frequency has not been attempted (ie. R4 to R2), and all focus on moving R0/1 to R2, though the same techniques would work to move to R3/4.
-== Shorting the Rod ==
+== Method 1: Shorting the Rod ==
-Shortinign the rods was attempted on the first modification of the R0 to R2 preselector.  The cap hats were removed and the center rods were ground down .270" on each rod.
+Shortening the rods was attempted on the first modification of the R0 to R2 preselector.  The cap hats were removed and the center rods were ground down .270" on each rod.
 This became a problem as the rods are made of silver plated copper plated aluminum, which makes grinding a hard thing to do.  It removed the tinned part of the rods where they solder to the cap hats, and the alignment "key" notched into the top of the rods.   The final result was a filter which had a bit more ripple and wider than desired, but with good insertion loss.
@@ Line 74: / Line 72: @@
 I suspect the width was changed mostly due to moving the cap hats lower in the housing.
-[[File:R0 cut down tubes.jpg|thumb|R0 preseletor during modification.]]
+<gallery mode=packed widths=200px heights=200px class="center">
-[[File:R0 post mod drills.jpg|thumb|Quantar R0 converted to R2 by cutting tubes showing post modification drilling to lower capacitance]]
+Over all this method works, but it's much easier to cut the hats down in length.
-[[File:Quantar preselector R0 to R2 tube cutting mod.png|thumb|Quantar R0 converted to R2 via tub cutting sweep]]
+== Method 2: shortening the cap length ==
-[[File:QUANTAR R0 CONVERT OVERLAY ON R2.png|thumb|R0 converted to R2 by tube cutting over lay on real R2]]
+This is the preferred method to raise the frequency as it's more in line with the construction Motorola uses.

@@ Line 1: / Line 1: @@
 = Basics =
 The UHF preselector is a 3 pole, low insertion loss (1.2 dB) 4 MHz wide filter.  In practice this is closer to 5MHz wide.
 The preselector varies based on the band of the RX as follows

@@ Line 24: / Line 24: @@
 The internal design of the preselector is basically a tubular inductor and a top capacitance hat.  The center of this hat/inductor has a hole into which the tuning screws slide in to/out of.  The R0 preselector has a much longer screw, and the front panel has a protective metal part protecting the protruding parts.
-[[File:R0 Rx front.jpg|thumb|Range 0 Receiver front]]
+<gallery  widths=300px heights=300px class="center">
 The bottom of the preselector has T10 size screws on it and they need to be tightened and loosened in order of the numbers on the bottom plate.  Once apart the variance in the length of the cap hat should be noticed showing the range of the preselector.
@@ Line 42: / Line 44: @@
 |}
-[[File:UHF Preselector diagram.png|thumb|UHF Preselector diagram]]
+<gallery mode=packed widths=200px heights=200px class="center">
 = Modification =
@@ Line 56: / Line 73: @@
 I suspect the width was changed mostly due to moving the cap hats lower in the housing.