EXHIBIT 10.11

            RIDER TO CONSOLIDATED, AMENDED AND RESTATED DEED OF LEASE
                                 RIDER NO. THREE


 THIS RIDER TO CONSOLIDATED AMENDED AND RESTATED DEED OF LEASE AGREEMENT, made
this 15 day of May,  1998 by and between A & A Fairfax Four L.L.C.  as successor
in interest to The Variable Annuity Life Insurance Company (hereinafter referred
to as "Landlord"), and Stanford  Telecommunications,  Inc. (hereinafter referred
to as "Tenant").

                                WITNESSETH THAT:

WHEREAS,  Landlord and Tenant entered into a CONSOLIDATED,  AMENDED AND RESTATED
DEED OF LEASE dated October 1, 1993 (hereinafter the "Lease"); and

WHEREAS,  Landlord  and Tenant  entered  into  Rider No. 1 to the  CONSOLIDATED,
AMENDED AND RESTATED DEED OF LEASE dated June of 1995; and,

WHEREAS,  Landlord  and Tenant  entered  into  Rider No. 2 to the  CONSOLIDATED,
AMENDED AND RESTATED DEED OF LEASE dated September 30 of 1996; and,

WHEREAS,  Landlord and Tenant desire to further modify the Lease so as to extend
the Lease under the terms as set forth herein.

NOW,  THEREFORE,  in  consideration  of Ten Dollars  ($10.00) and other good and
valuable  consideration,   the  receipt  and  sufficiency  of  which  is  hereby
acknowledged by the parties hereto, the parties hereto agree as follows:

1. Terms.  All terms used and not defined  herein shall have the same meaning as
set forth in the Lease.

2.  Premises.  The Premises as defined in the Lease,  shall be deemed to include
the Second  Expansion  Space (as defined in Section 4 herein)  effective July 1,
1998 and shall  total  79,659  rentable  square feet  subject to the  adjustment
provided in Section 6 herein.

3. Extension Term. The Term of the Lease currently expires on September 30, 1999
and the  parties  hereby  agree to extend  the Term of the Lease for a period of
Seven (7) years  terminating at 11:59 P.M. on September 30, 2006 (the "Extension
Term").

4. Additional Space.  Commencing July 1, 1998, Landlord shall deliver and Tenant
hereby accepts, a portion of the first floor comprising of 1,687 rentable square
feet of  additional  space  as  outlined  on the  attached  Exhibit  A  ("Second
Expansion Space").  For the period July 1, 1 998 through September 30, 1999, the
Base Rent for the Second Expansion Space shall be $1,000.00 per month.

5. Tenant's  Proportionate Share. Effective July 1, 1998, Tenant's Proportionate
Share of  Operating  Expenses and Real Estate Taxes as defined in Section 1.9 of
the  Lease  shall  be  increased  to  83.65%.  Tenant's  Proportionate  Share of
Operating Expenses and Real Estate Taxes shall be further adjusted in accordance
with Section 6.

6.  Subleased  Premises.  It is  understood  and  acknowledged  that  Tenant and
Lockheed Martin as successor in interest to Loral  Corporation have entered into
a Sublease  agreement  dated  August of 1994 (the  "Sublease").  The Sublease is
governed by a certain lease  agreement  between  Lockheed Martin as successor in
interest to Loral Corporation and Landlord,  as amended (hereinafter referred to
as the "Lockheed  Lease").  The Sublease is comprised of  approximately  13,521,
located on the third (3rd) floor of 

<PAGE>

the Building (the "Subleased Premises").  It is further understood that upon the
expiration of the Lockheed  Lease,  either through its natural  expiration or by
early  termination of the Lockheed Lease in accordance  with the terms contained
therein,  the Subleased Premises shall be incorporated into the Premises and the
rentable area which comprises the Premises shall be increased to 93,180 rentable
square feet. Accordingly, Tenant's Proportionate Share of Operating Expenses and
Real Estate  Taxes as defined in Section 1.9 of the Lease shall be  increased to
97.85%  immediately  upon the expiration of the Lockheed Lease. For the purposes
of the  schedule of Base Rent set forth in Section 7 herein,  it is assumed that
the  Sublease  shall  expire at its natural  expiration  of November  30,  2001.
Notwithstanding  anything to the  contrary,  in the event the Lockheed  Lease is
terminated  prior to its  natural  expiration  for any  reason  whatsoever,  the
Subleased  Premises shall then immediately be incorporated  into the Premises in
accordance  with this  paragraph and the base Rent schedule shall be adjusted so
as to  incorporate  the  Subleased  Premises.  The Base  Rent for the  Subleased
Premises at the  expiration  of the Lockheed  Lease shall be the then  escalated
rate for the Premises on a per square foot basis (see Section 7).
<TABLE>

7. Adjustment of Rent. In addition to all Base Rent and other sums to be paid by
the Tenant  pursuant to the Lease Tenant agrees to pay the following  amounts of
Base Rent for the Extension Term:
<CAPTION>
----------------------- -------------------- ------------------ --------------------- ---------------------
      LEASE YEAR             RENTABLE            BASE RENT             ANNUAL               MONTHLY
                            SQUARE FEET          PER S.F.            BASE RENT             BASE RENT
----------------------- -------------------- ------------------ --------------------- ---------------------
<S>                           <C>                 <C>              <C>                    <C>        
   10/1/99-9/30/00            79,659              $20.60           $1,640,975.40          $136,747.95
----------------------- -------------------- ------------------ --------------------- ---------------------
   10/1/00-9/31/01            79,659              $21.22           $1,690,204.66          $140,850.39
----------------------- -------------------- ------------------ --------------------- ---------------------
   10/1/01-1/30/01            79,659              $21.85           $1,740,910.80          $145,075.90
----------------------- -------------------- ------------------ --------------------- ---------------------
   12/1/01-9/30/02            93,180              $21.85           $2,036,406.04          $169,700.50
----------------------- -------------------- ------------------ --------------------- ---------------------
   10/1/02-9/30/03            93,180              $22.51           $2,097,498.22          $174,791.52
----------------------- -------------------- ------------------ --------------------- ---------------------
   10/1/03-9/30/04            93,180              $23.19           $2,160,423.16          $180,035.26
----------------------- -------------------- ------------------ --------------------- ---------------------
   10/1/04-9/30/05            93,180              $23.88           $2,225,235.86          $185,436.32
----------------------- -------------------- ------------------ --------------------- ---------------------
   10/1/05-9/30/06            93,180              $24.60           $2,291,992.94          $190,999.41
----------------------- -------------------- ------------------ --------------------- ---------------------
</TABLE>


For the purposes of the schedule  above,  it is assumed that the Sublease  shall
survive  until the natural  expiration of its term. In the event the Sublease is
terminated  prior to its  natural  expiration  for any  reason  whatsoever,  the
schedule above shall be adjusted to include the Subleased Premises.

8.  Improvements  to the Premises.  Tenant  accepts the Premises in its absolute
"as-is" condition. The cost of any additional improvements will be paid directly
by Tenant and shall be deemed  Additional  Rent as  defined  in the  Lease.  All
improvements  shall be  completed in  accordance  with  Sections  13.2 and 13.3.
Notwithstanding  the above,  Landlord  shall  contribute  a total of two hundred
twenty  thousand  dollars  ($220,000)  towards the cost of  improvements  to the
Premises (the "Allowance"). The Allowance shall be funded in accordance with the
following schedule; (I) Landlord shall provide $140,000 on or about September 1,
1999 and (ii) $80,000 at the conclusion of the fourth Lease Year for the Term so
extended (i.e.  September 30, 2003).  Each installment of the Allowance shall be
funded within 45 days of Tenant's written request to Landlord.

9. Assignment and Subletting. Notwithstanding anything contained in the Lease to
the  contrary,  Tenant and  Landlord  shall  share  equally in any  sublease  or
assignment  revenue which exceeds the Rent for the proposed  sublease  premises,
less the costs of Tenant's  reasonable  transaction fees directly  incurred as a
result of the proposed sublease/assignment. Tenant shall provide Landlord with a
detailed  accounting of all transaction fees (including  invoices from 3rd party
vendors/consultants) within thirty (30) days of the proposed sublease/assignment
effective date. It is specifically understood that the language contained herein
shall supersede the Lease
<PAGE>

10. Base Year for Operating Expenses and Real Estate Taxes.  Effective September
1, 1999, the Base Year for Operating  Expenses and Real Estate Taxes, as defined
in Section  1.8 of the Lease (as more  specifically  defined in Sections 7 and 8
respectively), shall be adjusted to reflect a Base Year cost of $7.20 per square
foot and upon such date all  references to the "Calendar  Year 1993" as the Base
Year shall be deleted.  As such,  Tenant  shall be required to pay its  Pro-Rata
share of Operating Expenses and Real Estate Taxes which exceed the new Base Year
amount (i.e.  $7.20 per s.f.) provided however that Tenant shall not be required
to make such  payment  prior to January 1,  2000.  All other  terms of the Lease
governing  Operating  Expenses and Real Estate  Taxes shall apply,  specifically
including any cap on Operating Expenses provided therein.

11. Option To Extend.  As long as Tenant has not been in Default more than three
(3) times  during the Term of the Lease as so extended  by this Rider No.  Three
and is not in an Event of Default under the Lease at the time of its exercise of
this option, Tenant shall have one (1) option to extend this Lease in accordance
with the provisions of this paragraph for an additional term of three (3) years,
on all the same terms and  conditions  with the  exception  of Base Rent payable
under Section 2 of the Lease,  which shall be Landlord's  then  prevailing  fair
market value being charged by landlord's for space reasonably  comparable to the
Premises.  If Tenant elects to exercise the foregoing option to extend, it shall
give  Landlord  written  notice of its  election  to do so on or before the date
which is two hundred and twenty (220) days prior to the  expiration  of the Term
of the  Lease,  but not prior to three  hundred  twenty  (320) days prior to the
expiration  of the Term of the Lease,  time being of the  essence,  which notice
shall also request that Landlord shall furnish Tenant with the base rent for the
extended term which shall be derived using Landlord's reasonable estimate of the
fair market rate for space  comparable to the Premises.  Landlord  shall furnish
Tenant  within  thirty (30) days of receipt of Tenant's  notice of exercise with
the base rent figure for the term  extension.  Provided,  however,  in the event
Landlord  and Tenant have not signed an  amendment  to this Lease for any reason
confirming  the extended  term of the Lease and setting  forth the base rent for
that term by a date  which is no less than one  hundred  and  eighty  (180) days
prior to the  expiration  of the Term of the Lease,  time being of the  essence,
then  Tenant's  extension  of the Lease  shall be deemed  null and void and this
Lease shall expire on the termination  date as if the above extension option had
not been exercised. This option to extend is personal to Tenant only, and is not
assignable.  Tenant has no option(s) to extend this Lease except as set forth in
this paragraph.


12. Brokerage Landlord and Tenant acknowledge that no real estate broker,  agent
or finder,  other than Cambridge Property Group Limited Partnership as Agent for
Landlord,   has  been  involved  in  procuring  or  otherwise  negotiating  this
transaction on either parties behalf. Further Tenant shall indemnify, defend and
hold  harmless  Landlord  against and from any claims made by any other agent or
finder claiming to represent Tenant.  Notwithstanding the above, Landlord agrees
to pay Cambridge Property Group Limited  Partnership a commission based upon the
terms contained in a separate written agreement between the parties.

13.  Ratification.  Except  as  specifically  modified  herein,  all  terms  and
conditions  of the Lease are hereby  ratified  by the  parties  hereto and shall
remain in full force and effect.



<PAGE>



IN WITNESS WHEREOF,  Landlord and Tenant have executed this Rider as of the date
first written above.


 WITNESS:                    LANDLORD:  A & A Fairfax Four L.L.C.
                             By:  Cambridge Asset Advisors Limited Partnership,
                             As Agent
                             By:  Cambridge Property Advisors, Inc., as General
                             Partner



                             /s/ Andrew J. Czekaj
                             --------------------
                             Mr. Andrew J. Czekaj
                             Chairman



 WITNESS:                    TENANT: Stanford Telecommunications, Inc.



                             /s/ Leonard Schuchman
                             ---------------------
                             Mr. Leonard Schuchman
                             Vice President